@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

/* ===== ANTIGRAVITY LIGHT THEME — Paper White & Calm Azure ===== */
:root {
    --primary: #3B82C4;
    --primary-hover: #2E6DA8;
    --primary-glow: rgba(59, 130, 196, 0.25);
    --primary-glow-subtle: rgba(59, 130, 196, 0.10);
    --secondary: #0D9488;
    --bg: #FBFBFA;
    --surface: #FFFFFF;
    --surface-glass: rgba(255, 255, 255, 0.72);
    --text-main: #1A202C;
    --text-muted: #64748B;
    --border: #E2E8F0;
    --border-glass: rgba(226, 232, 240, 0.7);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.03);
    --shadow: 0 8px 30px rgba(0, 0, 0, 0.06), 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.08), 0 8px 20px rgba(0, 0, 0, 0.04);
    --shadow-glow: 0 8px 40px rgba(59, 130, 196, 0.08), 0 4px 16px rgba(0, 0, 0, 0.05);
    --radius: 0.875rem;

    /* Compatibility aliases */
    --danger: #DC2626;
    --warning: #D97706;
    --text: var(--text-main);
    --text-light: var(--text-muted);

    /* Tint / accent background tokens */
    --primary-tint: rgba(59, 130, 196, 0.08);
    --primary-tint-light: rgba(59, 130, 196, 0.04);
    --primary-tint-border: rgba(59, 130, 196, 0.18);
    --primary-tint-text: #1E5A8A;
    --secondary-tint: rgba(13, 148, 136, 0.06);
    --secondary-tint-border: rgba(13, 148, 136, 0.15);
    --secondary-tint-text: #0F766E;
    --danger-tint: #FEF2F2;
    --danger-tint-border: rgba(220, 38, 38, 0.18);
    --danger-tint-text: #991B1B;
    --warning-tint: #FFFBEB;
    --warning-tint-border: rgba(217, 119, 6, 0.2);
    --warning-tint-text: #92400E;
    --neutral-tint: #F1F5F9;
    --input-bg: #FFFFFF;
    --tooltip-bg: #1E293B;
    --tooltip-color: #F8FAFC;
    --emerald-tint: rgba(13, 148, 136, 0.06);
    --emerald-tint-text: #0D9488;

    /* Glassmorphism tokens — light mode frosted glass */
    --glass-blur: 18px;
    --glass-border: 1px solid rgba(255, 255, 255, 0.5);
    --glass-highlight: inset 0 1px 0 rgba(255, 255, 255, 0.7);

    /* Jewel-tone syntax highlighting */
    --syntax-keyword: #7C3AED;
    --syntax-string: #059669;
    --syntax-number: #B45309;
    --syntax-comment: #94A3B8;
    --syntax-function: #2563EB;
    --syntax-variable: #BE185D;
    --syntax-operator: #1A202C;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg);
    color: var(--text-main);
    line-height: 1.6;
    min-height: 100vh;
    padding: 2rem;
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
    position: relative;
}

/* Ambient radial glow behind content — soft warm azure halos */
body::before {
    content: '';
    position: fixed;
    top: -20%;
    left: 50%;
    transform: translateX(-50%);
    width: 1000px;
    height: 1000px;
    background: radial-gradient(circle, rgba(59, 130, 196, 0.06) 0%, rgba(59, 130, 196, 0.02) 40%, transparent 70%);
    pointer-events: none;
    z-index: 0;
}

body::after {
    content: '';
    position: fixed;
    bottom: -30%;
    right: -10%;
    width: 800px;
    height: 800px;
    background: radial-gradient(circle, rgba(13, 148, 136, 0.04) 0%, transparent 65%);
    pointer-events: none;
    z-index: 0;
}

/* Particle canvas layer */
#particleCanvas {
    position: fixed;
    inset: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 0;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

/* Floating keyframes for antigravity effect */
@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-8px); }
}

@keyframes floatSlow {
    0%, 100% { transform: translateY(0px) rotate(0deg); }
    50% { transform: translateY(-5px) rotate(0.5deg); }
}

@keyframes glowPulse {
    0%, 100% { box-shadow: 0 0 20px rgba(59, 130, 196, 0.06), var(--shadow); }
    50% { box-shadow: 0 0 35px rgba(59, 130, 196, 0.1), var(--shadow); }
}

@keyframes borderShimmer {
    0% { border-color: rgba(59, 130, 196, 0.1); }
    50% { border-color: rgba(59, 130, 196, 0.2); }
    100% { border-color: rgba(59, 130, 196, 0.1); }
}

/* HEADER */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 3rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border);
    position: relative;
}

header h1 {
    font-size: 2rem;
    font-weight: 800;
    letter-spacing: -0.025em;
    color: var(--text-main);
    background: linear-gradient(135deg, #2563EB, #3B82C4, #0D9488);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: none;
    filter: drop-shadow(0 0 12px rgba(59, 130, 196, 0.15));
}

header p {
    color: var(--text-muted);
    font-size: 1rem;
    margin-top: 0.25rem;
    letter-spacing: 0.02em;
}

/* MENU */
.menu-container { position: relative; }

.menu-btn {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    color: var(--text-main);
    border: 1px solid var(--border-glass);
    padding: 0.6rem 1.25rem;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-sm), var(--glass-highlight);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.menu-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    box-shadow: 0 4px 16px var(--primary-glow-subtle), var(--shadow);
    transform: translateY(-2px);
}

.menu-dropdown {
    display: none;
    position: absolute;
    right: 0;
    top: 125%;
    width: 220px;
    background: var(--surface-glass);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg), var(--glass-highlight);
    padding: 0.5rem;
    z-index: 50;
    opacity: 0;
    transform: translateY(-10px);
    transition: opacity 0.3s, transform 0.3s;
}

.menu-dropdown.show {
    display: block;
    opacity: 1;
    transform: translateY(0);
}

.menu-item {
    display: block;
    width: 100%;
    text-align: left;
    padding: 0.6rem 1rem;
    margin-bottom: 0.25rem;
    background: transparent;
    border: none;
    border-radius: 0.5rem;
    color: var(--text-main);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.15s;
}

.menu-item:hover {
    background-color: var(--primary-tint);
    color: var(--primary);
}

.menu-item[aria-current="page"] {
    background-color: var(--primary-tint);
    color: var(--primary);
    font-weight: 700;
    box-shadow: inset 2px 0 0 var(--primary);
}

.tab-content { display: none; animation: fadeInFloat 0.6s cubic-bezier(0.22, 0.61, 0.36, 1); }
.tab-content.active { display: block; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeInFloat {
    from { opacity: 0; transform: translateY(20px) scale(0.98); }
    to { opacity: 1; transform: translateY(0) scale(1); }
}

/* CARDS & SECTIONS — Glass Panels */
.card {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border-radius: var(--radius);
    box-shadow: var(--shadow-glow), var(--glass-highlight);
    padding: 2rem;
    margin-bottom: 2rem;
    border: 1px solid var(--border-glass);
    transition: all 0.4s ease;
    position: relative;
    overflow: hidden;
    /* animation: floatSlow 6s ease-in-out infinite; */
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(59, 130, 196, 0.12), transparent);
}

.card:hover {
    border-color: rgba(59, 130, 196, 0.15);
    box-shadow: 0 12px 50px rgba(0, 0, 0, 0.08), 0 0 30px rgba(59, 130, 196, 0.06);
    transform: translateY(-3px);
}

.card h2 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-main);
    margin-bottom: 0.5rem;
    letter-spacing: -0.025em;
}

.card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 2rem 0 1rem 0;
    color: var(--text-main);
}

.section-tag {
    display: inline-block;
    background: linear-gradient(135deg, var(--primary-tint), var(--primary-tint-light));
    color: var(--primary);
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    padding: 0.3rem 0.85rem;
    border-radius: 99px;
    margin-bottom: 0.75rem;
    letter-spacing: 0.08em;
    border: 1px solid var(--primary-tint-border);
    box-shadow: 0 2px 8px var(--primary-glow-subtle);
}

.card-subtitle {
    color: var(--text-muted);
    margin-top: 0.25rem;
}

.note-box {
    background: linear-gradient(135deg, var(--primary-tint-light), var(--primary-tint));
    border: 1px solid var(--primary-tint-border);
    border-radius: var(--radius);
    padding: 1rem 1.25rem;
    color: var(--text-main);
    margin: 1.25rem 0;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.5);
}

.highlight-cell {
    background: var(--secondary-tint);
    color: var(--secondary-tint-text);
    font-weight: 700;
    border-radius: 0.5rem;
}

/* CALLBACK-STYLE FORM */
.callback-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-main);
    margin-bottom: 2rem;
}

.callback-form {
    padding: 0;
}

.cb-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.25rem;
    margin-bottom: 1.25rem;
}

.cb-row-single {
    grid-template-columns: 1fr;
}

.cb-field {
    position: relative;
}

.cb-field input {
    width: 100%;
    padding: 1.25rem 1rem 0.5rem;
    border: 1px solid var(--border-glass);
    border-radius: 0.5rem;
    font-size: 1rem;
    font-family: 'Inter', sans-serif;
    background: var(--input-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
    transition: border-color 0.3s, box-shadow 0.3s;
    outline: none;
}

.cb-field input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow-subtle), 0 0 15px var(--primary-glow-subtle);
}

.cb-field label {
    position: absolute;
    top: 50%;
    left: 1rem;
    transform: translateY(-50%);
    font-size: 1rem;
    color: var(--text-muted);
    pointer-events: none;
    transition: all 0.2s ease;
    background: transparent;
    padding: 0 0.25rem;
}

/* Float label up when input is focused or has content */
.cb-field input:focus + label,
.cb-field input:not(:placeholder-shown) + label {
    top: 0.45rem;
    transform: translateY(0);
    font-size: 0.72rem;
    color: var(--primary);
    font-weight: 500;
}

.cb-submit-wrap {
    display: flex;
    justify-content: flex-end;
    margin-top: 0.5rem;
    margin-bottom: 1.5rem;
}

.cb-submit {
    background: linear-gradient(135deg, var(--primary), var(--primary-hover));
    color: #fff;
    padding: 0.85rem 2.5rem;
    border: none;
    border-radius: 0.5rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    box-shadow: 0 4px 16px var(--primary-glow), var(--shadow-sm);
}

.cb-submit:hover {
    background: linear-gradient(135deg, var(--primary-hover), #245D94);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px var(--primary-glow), var(--shadow);
}

.cb-submit:active {
    transform: translateY(0);
}

@media (max-width: 600px) {
    .cb-row { grid-template-columns: 1fr; }
}

.results-display {
    background: var(--secondary-tint);
    border: 1px solid var(--secondary-tint-border);
    border-radius: 0.5rem;
    padding: 1.5rem;
    min-height: 100px;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

.results-display:empty::before {
    content: '💡 Enter networking data above to see intelligent analysis';
    color: var(--text-muted);
    display: block;
    text-align: center;
}

.empty-state {
    color: var(--text-muted);
    text-align: center;
    margin: 0;
}

/* FORMS */
.form-group {
    margin-bottom: 1.5rem;
}

.form-label {
    display: block;
    margin-bottom: 0.75rem;
    font-weight: 600;
    color: var(--text-main);
}

.form-hint {
    display: block;
    font-weight: 400;
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-top: 0.25rem;
}

.form-textarea {
    width: 100%;
    padding: 1rem;
    border: 2px solid var(--border);
    border-radius: 0.5rem;
    font-size: 0.95rem;
    font-family: 'Courier New', monospace;
    line-height: 1.6;
    transition: all 0.3s;
    background: var(--input-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
    resize: vertical;
    min-height: 140px;
}

.form-textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow-subtle), 0 0 15px var(--primary-glow-subtle);
    background: var(--input-bg);
}

.form-textarea::placeholder {
    color: var(--text-muted);
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 1.5rem;
    margin-bottom: 1.5rem;
}

.btn-primary {
    flex: 1;
    background: linear-gradient(135deg, var(--primary), var(--primary-hover));
    color: white;
    padding: 0.875rem 1.75rem;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 1.05rem;
    border: none;
    cursor: pointer;
    transition: all 0.3s;
    box-shadow: 0 4px 16px var(--primary-glow), var(--shadow-sm);
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-hover), #245D94);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px var(--primary-glow), var(--shadow);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
    padding: 0.875rem 1.5rem;
    border-radius: 0.5rem;
    font-weight: 600;
    border: 2px solid var(--border-glass);
    cursor: pointer;
    transition: all 0.3s;
}

.btn-secondary:hover {
    background: var(--neutral-tint);
    border-color: var(--text-muted);
}

.results-container {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 2px solid var(--border);
}

.calc-input-group input[type="text"],
.calc-input-group input[type="number"],
.interactive-calculator input[type="text"],
.interactive-calculator input[type="number"],
select {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-glass);
    border-radius: 0.5rem;
    font-size: 1rem;
    font-family: 'Inter', monospace;
    transition: all 0.3s;
    background: var(--input-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
}

.calc-input-group input:focus,
.interactive-calculator input:focus,
select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow-subtle), 0 0 15px var(--primary-glow-subtle);
    background: var(--input-bg);
}

button {
    background: linear-gradient(135deg, var(--primary), var(--primary-hover));
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 0.5rem;
    font-weight: 600;
    border: none;
    cursor: pointer;
    transition: all 0.3s;
    box-shadow: 0 4px 12px var(--primary-glow-subtle), var(--shadow-sm);
}

button:hover {
    background: linear-gradient(135deg, var(--primary-hover), #245D94);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--primary-glow), var(--shadow);
}

/* TABLES */
.edu-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin: 1.5rem 0;
    min-width: 100%;
}

.edu-table th {
    background-color: var(--bg);
    font-weight: 600;
    text-align: left;
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border);
    color: var(--text-muted);
    text-transform: uppercase;
    font-size: 0.75rem;
    letter-spacing: 0.05em;
}

.edu-table td {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border);
    color: var(--text-main);
    font-variant-numeric: tabular-nums;
}

.edu-table tr:last-child td { border-bottom: none; }
.edu-table tr:hover td:not(.highlight-cell) { background-color: var(--bg); }

/* SPECIAL COMPONENTS */
.decoder-grid {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 0.75rem;
    margin: 2rem 0;
}

.decoder-box {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--border-glass);
    border-radius: 0.5rem;
    padding: 1rem 0.5rem;
    text-align: center;
    transition: all 0.3s ease;
    box-shadow: var(--glass-highlight);
}

.decoder-box:hover {
    border-color: rgba(59, 130, 196, 0.3);
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(59, 130, 196, 0.1), var(--shadow);
}

.decoder-bit { font-size: 0.75rem; color: var(--text-muted); margin-bottom: 0.25rem; font-weight: 500; }
.decoder-value { font-size: 1.25rem; font-weight: 700; color: var(--primary); }

.step-container {
    border-left: 3px solid var(--primary);
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    padding: 1.5rem;
    margin: 1.5rem 0;
    border-radius: 0 0.5rem 0.5rem 0;
    box-shadow: var(--glass-highlight), -2px 0 10px var(--primary-glow-subtle);
}

.step-number {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    width: 28px;
    height: 28px;
    background-color: var(--primary);
    color: white;
    border-radius: 50%;
    font-size: 0.85rem;
    font-weight: 700;
    margin-right: 0.75rem;
}

.example-box {
    background: var(--neutral-tint);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin: 2rem 0;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    box-shadow: var(--glass-highlight);
}

.example-title {
    color: var(--primary);
    font-weight: 700;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.formula-box {
    background: var(--primary-tint-light);
    border: 1px dashed var(--primary-tint-border);
    color: var(--primary);
    padding: 1.5rem;
    text-align: center;
    border-radius: var(--radius);
    font-family: 'Courier New', monospace;
    font-weight: 700;
    font-size: 1.1rem;
    margin: 1.5rem 0;
}

/* Converter result animations */
@keyframes cellPopIn {
    from { opacity: 0; transform: scale(0.7) translateY(8px); }
    to   { opacity: 1; transform: scale(1) translateY(0); }
}
@keyframes formulaSlideUp {
    from { opacity: 0; transform: translateY(12px); }
    to   { opacity: 1; transform: translateY(0); }
}
.calc-result .edu-table th,
.calc-result .edu-table td {
    opacity: 0;
    animation: cellPopIn 0.35s ease forwards;
}
.calc-result .formula-box {
    opacity: 0;
    animation: formulaSlideUp 0.4s ease forwards;
}
.calc-result .converter-answer {
    opacity: 0;
    animation: formulaSlideUp 0.4s ease forwards;
}

.calc-result {
    background: var(--secondary-tint);
    border: 1px solid var(--secondary-tint-border);
    color: var(--secondary-tint-text);
    padding: 1.5rem;
    border-radius: var(--radius);
    margin-top: 1.5rem;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

/* ---------- Decimal-to-Binary Steps Table ---------- */
.dec-steps-details {
    margin-top: 1rem;
    text-align: left;
}

.dec-steps-details summary {
    cursor: pointer;
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--primary);
    padding: 0.5rem 0;
    user-select: none;
    transition: color 0.2s;
}

.dec-steps-details summary:hover {
    color: var(--primary-hover);
}

.dec-steps-table-wrap {
    overflow-x: auto;
    margin-top: 0.75rem;
}

.dec-steps-table {
    background: var(--surface-glass);
    border-radius: var(--radius);
    overflow: hidden;
    border: 1px solid var(--border-glass);
}

.dec-steps-table th {
    text-align: center;
    white-space: nowrap;
}

.dec-steps-table td {
    text-align: center;
    font-variant-numeric: tabular-nums;
}

.dec-steps-table .step-fit td {
    background-color: var(--secondary-tint);
    color: var(--secondary-tint-text);
}

.dec-steps-table .step-nofit td {
    background-color: transparent;
    color: var(--text-muted);
}

.step-icon {
    font-weight: 600;
    white-space: nowrap;
}

.step-icon.fit {
    color: var(--secondary);
}

.step-icon.nofit {
    color: var(--danger);
}

.step-bit {
    font-family: 'Courier New', monospace;
    font-weight: 700;
    font-size: 1.1rem;
}

.interactive-calculator {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--border-glass);
    border-radius: var(--radius);
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-glow), var(--glass-highlight);
    position: relative;
    overflow: hidden;
}

.interactive-calculator::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(59, 130, 196, 0.1), transparent);
}

.interactive-calculator h4 {
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
    color: var(--text-main);
}

.calc-input-group {
    display: flex;
    gap: 1rem;
    align-items: center;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.calc-input-group label {
    font-weight: 500;
    min-width: 150px;
}

/* SUBNET VISUALIZATION */
.subnet-visual {
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin: 1.5rem 0;
    box-shadow: var(--glass-highlight);
}

.subnet-visual h4 {
    margin-bottom: 1rem;
    font-size: 1rem;
    color: var(--text-main);
    text-align: center;
}

.subnet-bar-container {
    display: flex;
    width: 100%;
    height: 60px;
    border-radius: 0.5rem;
    overflow: hidden;
    box-shadow: var(--shadow);
    margin-bottom: 1rem;
}

.subnet-segment {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 0.5rem;
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    text-align: center;
    border-right: 2px solid white;
    transition: all 0.3s ease;
    cursor: pointer;
    position: relative;
    min-width: 0;
}

.subnet-segment:last-child {
    border-right: none;
}

.subnet-segment:hover {
    filter: brightness(1.2);
    transform: translateY(-2px);
    z-index: 10;
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

.subnet-segment-label {
    font-size: 0.7rem;
    opacity: 0.9;
}

.subnet-legend {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 0.75rem;
    margin-top: 1rem;
}

.subnet-legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem;
    background: var(--surface-glass);
    border-radius: 0.375rem;
    font-size: 0.85rem;
    border: 1px solid var(--border-glass);
}

.subnet-legend-color {
    width: 20px;
    height: 20px;
    border-radius: 0.25rem;
    flex-shrink: 0;
}

/* BLOCK DIVIDER (Intervals tab) */
.divider-slider-wrap {
    margin: 1rem 0;
}

.divider-slider-wrap label {
    font-weight: 500;
    font-size: 0.95rem;
    display: block;
    margin-bottom: 0.5rem;
}

.divider-slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 8px;
    border-radius: 4px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    outline: none;
    cursor: pointer;
}

.divider-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--surface);
    border: 3px solid var(--primary);
    box-shadow: 0 2px 8px var(--primary-glow), var(--shadow-sm);
    cursor: grab;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.divider-slider::-webkit-slider-thumb:hover {
    transform: scale(1.15);
    box-shadow: 0 4px 16px var(--primary-glow), var(--shadow);
}

.divider-slider::-moz-range-thumb {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--surface);
    border: 3px solid var(--primary);
    box-shadow: var(--shadow);
    cursor: grab;
}

.divider-slider-ticks {
    display: flex;
    justify-content: space-between;
    padding: 0.25rem 0;
    font-size: 0.72rem;
    color: var(--text-muted);
    font-weight: 600;
    font-variant-numeric: tabular-nums;
}

.divider-stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.75rem;
    margin: 1rem 0;
}

.divider-stat {
    text-align: center;
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border-radius: 0.5rem;
    padding: 0.75rem 0.5rem;
    border: 1px solid var(--border-glass);
    box-shadow: var(--glass-highlight);
}

.divider-stat-val {
    display: block;
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--primary);
    line-height: 1.2;
}

.divider-stat-lbl {
    display: block;
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 0.2rem;
    font-weight: 500;
}

/* 32-BIT STRIP */
.bit-strip {
    display: flex;
    width: 100%;
    margin-bottom: 1rem;
    border-radius: 0.375rem;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.bit-cell {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    height: 32px;
    font-size: 0.7rem;
    font-weight: 700;
    font-family: 'Inter', monospace;
    border-right: 1px solid rgba(255,255,255,0.4);
    user-select: none;
    cursor: pointer;
    position: relative;
    transition: filter 0.15s ease, transform 0.15s ease;
}

.bit-cell:hover {
    filter: brightness(1.25);
    transform: scaleY(1.15);
    z-index: 5;
}

.bit-cell:last-child {
    border-right: none;
}

.bit-cell--network {
    background: #3730a3;
    color: #fff;
}

.bit-cell--subnet {
    background: #047857;
    color: #fff;
}

.bit-cell--host {
    background: #E2E8F0;
    color: #64748B;
}

/* Bit cell rich tooltip */
.bit-cell[data-bit-tooltip]::after {
    content: attr(data-bit-tooltip);
    position: absolute;
    bottom: calc(100% + 8px);
    left: 50%;
    transform: translateX(-50%);
    background: var(--tooltip-bg);
    color: var(--tooltip-color);
    font-size: 0.72rem;
    font-weight: 500;
    padding: 0.4rem 0.7rem;
    border-radius: 0.375rem;
    white-space: nowrap;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.2s ease;
    z-index: 30;
    box-shadow: 0 3px 10px rgba(0,0,0,0.3);
}

.bit-cell[data-bit-tooltip]::before {
    content: '';
    position: absolute;
    bottom: calc(100% + 2px);
    left: 50%;
    transform: translateX(-50%);
    border: 5px solid transparent;
    border-top-color: var(--tooltip-bg);
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.2s ease;
    z-index: 30;
}

.bit-cell[data-bit-tooltip]:hover::after,
.bit-cell[data-bit-tooltip]:hover::before {
    opacity: 1;
}

.bit-strip-labels {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    margin-bottom: 0.5rem;
}

.bit-label {
    font-size: 0.8rem;
    font-weight: 600;
    padding: 0.2rem 0.6rem;
    border-radius: 0.25rem;
}

.bit-label--network {
    background: var(--primary-tint-light);
    color: var(--primary);
}

.bit-label--subnet {
    background: var(--emerald-tint);
    color: var(--emerald-tint-text);
}

.bit-label--host {
    background: var(--neutral-tint);
    color: var(--text-muted);
}

/* SUBNET SEGMENT – position context for JS popup */
.subnet-segment {
    position: relative;
    cursor: pointer;
}

/* RESPONSIVE */
@media (max-width: 768px) {
    body { padding: 1rem; }
    .decoder-grid { grid-template-columns: repeat(4, 1fr); }
    header { flex-direction: column; align-items: flex-start; gap: 1rem; }
    .menu-container { align-self: flex-end; }
    .subnet-bar-container { height: 80px; flex-wrap: wrap; }
    .subnet-segment { font-size: 0.65rem; min-width: 60px; }
    .bit-cell { height: 24px; font-size: 0.6rem; }
    .bit-strip-labels { gap: 0.5rem; }
    .bit-label { font-size: 0.7rem; }
    .divider-stats-grid { grid-template-columns: repeat(2, 1fr); }
    .challenge-score { flex-wrap: wrap; gap: 0.5rem; }
    .challenge-score-item { min-width: 80px; }
    .challenge-input-row { flex-wrap: wrap; }
    .challenge-input-row input { min-width: 0; }
    .challenge-hint-btn { flex: 1 1 100%; }
}

/* SUBNET CONTEXT BAR (unused space segments — legacy fallback) */
.subnet-context-unused {
    display: flex;
    align-items: center;
    justify-content: center;
    background: #E2E8F0;
    color: #94A3B8;
    font-size: 0.7rem;
    font-weight: 500;
    border-right: 2px solid white;
}

/* === REDESIGNED SUBNET-IN-CONTEXT SECTION === */
.subnet-context-visual {
    background: var(--primary-tint-light);
    border: 1px solid var(--primary-tint-border);
}

/* Range labels above the bar */
.ctx-bar-range {
    display: flex;
    justify-content: space-between;
    font-size: 0.72rem;
    font-family: 'Inter', monospace;
    color: var(--text-muted);
    margin-bottom: 0.25rem;
    padding: 0 2px;
}

/* Context bar segments */
.ctx-bar {
    border-radius: 0.5rem;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    margin-bottom: 0.5rem;
}

.ctx-segment {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    min-width: 0;
    overflow: hidden;
    transition: filter 0.2s ease;
}

.ctx-segment--before,
.ctx-segment--after {
    background: #E2E8F0;
    border-right: 2px solid white;
    cursor: pointer;
    position: relative;
}

.ctx-segment--before:hover,
.ctx-segment--after:hover {
    background: #CBD5E1;
}



.ctx-segment-label {
    font-size: 0.72rem;
    font-weight: 600;
    color: #64748B;
    line-height: 1.3;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    padding: 0 6px;
}

.ctx-segment--active {
    background: #4f46e5;
    color: #fff;
    position: relative;
    border-right: 2px solid white;
    z-index: 2;
    box-shadow: 0 0 0 2px rgba(79, 70, 229, 0.35);
    cursor: pointer;
}

.ctx-segment--active:hover {
    filter: brightness(1.15);
}

.ctx-active-label {
    font-size: 0.72rem;
    font-weight: 700;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    padding: 0 6px;
}

/* JS-powered popup tooltip (replaces CSS pseudo-element tooltips) */
.ctx-popup {
    position: fixed;
    display: none;
    background: var(--tooltip-bg);
    color: var(--tooltip-color);
    font-size: 0.78rem;
    padding: 0.65rem 0.85rem;
    border-radius: 0.5rem;
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.2s ease;
    z-index: 9999;
    box-shadow: 0 4px 16px rgba(0,0,0,0.3);
    white-space: nowrap;
    min-width: 200px;
    max-width: 360px;
    text-align: left;
    line-height: 1.55;
}

.ctx-popup.show { opacity: 1; }

.ctx-popup-title {
    font-weight: 700;
    font-size: 0.82rem;
    margin-bottom: 0.3rem;
    border-bottom: 1px solid rgba(255,255,255,0.15);
    padding-bottom: 0.3rem;
}

.ctx-popup-line {
    font-weight: 400;
    font-size: 0.75rem;
    opacity: 0.92;
}

.ctx-popup-arrow {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    border: 6px solid transparent;
    border-top-color: var(--tooltip-bg);
}

/* Keep the bar container positioned for popup */
.ctx-bar {
    position: relative;
    overflow: visible !important;
}

/* Legend */
.ctx-legend {
    display: flex;
    gap: 1.25rem;
    flex-wrap: wrap;
    justify-content: center;
    margin-top: 0.6rem;
    margin-bottom: 0.25rem;
}

.ctx-legend-item {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.78rem;
    color: var(--text-muted);
    font-weight: 500;
}

.ctx-legend-swatch {
    display: inline-block;
    width: 14px;
    height: 14px;
    border-radius: 3px;
    flex-shrink: 0;
    border: 1px solid rgba(0,0,0,0.08);
}

/* Caption */
.ctx-caption {
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
    line-height: 1.5;
}

/* Bit-strip color legend (explains N/S/H meaning) */
.bit-color-legend {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    margin-bottom: 1rem;
    padding: 0.65rem 0.85rem;
    background: var(--neutral-tint);
    border-radius: 0.375rem;
    border: 1px solid var(--border);
}

.bit-color-legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.78rem;
    color: var(--text-main);
    line-height: 1.4;
}

.bit-color-swatch {
    display: inline-block;
    width: 18px;
    height: 18px;
    border-radius: 3px;
    flex-shrink: 0;
}

/* Responsive overrides for context bar */
@media (max-width: 768px) {
    .ctx-active-label { font-size: 0.65rem; }
    .ctx-segment-label { font-size: 0.6rem; }
    .ctx-bar-range { font-size: 0.65rem; }
    .ctx-legend { gap: 0.75rem; }
    .ctx-legend-item { font-size: 0.72rem; }
    .bit-color-legend-item { font-size: 0.72rem; }
    .bit-color-swatch { width: 14px; height: 14px; }
}

/* CHALLENGE / QUIZ TAB */
.challenge-score {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    justify-content: center;
}

.challenge-score-item {
    text-align: center;
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid var(--border-glass);
    border-radius: 0.5rem;
    padding: 0.75rem 1.25rem;
    min-width: 100px;
    box-shadow: var(--glass-highlight);
}

.challenge-score-val {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    line-height: 1.2;
}

.challenge-score-val--streak { color: var(--primary); }
.challenge-score-val--correct { color: var(--secondary); }
.challenge-score-val--total { color: var(--text-muted); }

.challenge-score-lbl {
    display: block;
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 0.15rem;
    font-weight: 500;
}

.challenge-question-card {
    background: linear-gradient(135deg, var(--primary-tint-light), var(--primary-tint));
    border: 2px solid var(--primary-tint-border);
    border-radius: var(--radius);
    padding: 1.75rem;
    text-align: center;
    margin-bottom: 1.5rem;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    box-shadow: 0 4px 20px var(--primary-glow-subtle), var(--glass-highlight);
}

.challenge-question-card h3 {
    margin: 0 0 0.5rem 0;
    font-size: 1.4rem;
    color: var(--primary);
}

.challenge-question-card p {
    font-size: 1.1rem;
    color: var(--text-main);
    margin: 0.25rem 0;
}

.challenge-question-type {
    display: inline-block;
    background: var(--primary);
    color: #fff;
    font-size: 0.8rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    border-radius: 99px;
    margin-top: 0.75rem;
}

.challenge-input-row {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.challenge-input-row input {
    flex: 1;
    padding: 0.85rem 1rem;
    border: 2px solid var(--border-glass);
    border-radius: 0.5rem;
    font-size: 1.05rem;
    font-family: 'Inter', monospace;
    transition: border-color 0.3s, box-shadow 0.3s;
    outline: none;
    background: var(--input-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
}

.challenge-input-row input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow-subtle), 0 0 15px var(--primary-glow-subtle);
}

.challenge-feedback {
    border-radius: var(--radius);
    padding: 1.25rem;
    margin-top: 1rem;
    animation: fadeIn 0.3s ease;
}

.challenge-feedback--correct {
    background: var(--secondary-tint);
    border: 2px solid var(--secondary-tint-border);
    color: var(--secondary-tint-text);
}

.challenge-feedback--incorrect {
    background: var(--danger-tint);
    border: 2px solid var(--danger-tint-border);
    color: var(--danger-tint-text);
}

/* Challenge Options Row (timer toggle) */
.challenge-options-row {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.challenge-toggle {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    user-select: none;
}

.challenge-toggle input {
    display: none;
}

.challenge-toggle-slider {
    position: relative;
    width: 40px;
    height: 22px;
    background: var(--border);
    border-radius: 99px;
    transition: background 0.2s;
}

.challenge-toggle-slider::after {
    content: '';
    position: absolute;
    top: 3px;
    left: 3px;
    width: 16px;
    height: 16px;
    background: #fff;
    border-radius: 50%;
    transition: transform 0.2s;
    box-shadow: 0 1px 3px rgba(0,0,0,0.15);
}

.challenge-toggle input:checked + .challenge-toggle-slider {
    background: var(--primary);
}

.challenge-toggle input:checked + .challenge-toggle-slider::after {
    transform: translateX(18px);
}

.challenge-toggle-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-main);
}

/* Challenge Timer */
.challenge-timer-wrap {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1.25rem;
    padding: 0 0.25rem;
}

.challenge-timer-text {
    font-weight: 700;
    font-size: 0.95rem;
    min-width: 36px;
    color: var(--text-muted);
    text-align: center;
    font-variant-numeric: tabular-nums;
    transition: color 0.3s;
}

.challenge-timer-bar {
    flex: 1;
    height: 8px;
    background: var(--border);
    border-radius: 99px;
    overflow: hidden;
}

.challenge-timer-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 99px;
    transition: width 1s linear, background-color 0.5s;
}

.challenge-timer-fill.timer-warning {
    background: var(--warning);
}

.challenge-timer-fill.timer-danger {
    background: var(--danger);
}

.challenge-timer-text.timer-warning {
    color: var(--warning);
}

.challenge-timer-text.timer-danger {
    color: var(--danger);
}

/* Extend Time Button */
.challenge-extend-btn {
    white-space: nowrap;
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 2px solid var(--border-glass);
    font-weight: 700;
    font-size: 0.8rem;
    padding: 0.3rem 0.75rem;
    border-radius: 99px;
    cursor: pointer;
    color: var(--primary);
    transition: all 0.3s;
    flex-shrink: 0;
}

.challenge-extend-btn:hover {
    border-color: var(--primary);
    background: var(--primary-tint-light);
    box-shadow: 0 2px 10px var(--primary-glow-subtle);
}

/* Skip Button */
.challenge-skip-btn {
    white-space: nowrap;
    background: var(--surface-glass) !important;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 2px solid var(--border-glass);
    font-weight: 600;
    font-size: 0.9rem;
    padding: 0.6rem 1rem;
    border-radius: 0.5rem;
    cursor: pointer;
    color: var(--text-muted);
    transition: all 0.3s;
}

.challenge-skip-btn:hover:not(:disabled) {
    border-color: var(--text-muted);
    color: var(--text-main);
}

.challenge-skip-btn:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

/* Skipped feedback */
.challenge-feedback--skipped {
    background: var(--neutral-tint);
    border: 2px solid var(--border);
    color: var(--text-muted);
}

/* Challenge Hint */
.challenge-hint-btn {
    white-space: nowrap;
    background: var(--surface-glass) !important;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 2px solid var(--border-glass);
    font-weight: 600;
    font-size: 0.9rem;
    padding: 0.6rem 1rem;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.3s;
}

.challenge-hint-btn:hover:not(:disabled) {
    border-color: var(--warning);
    color: #b45309;
}

.challenge-hint-btn:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

.challenge-hint-box {
    margin-top: 0.75rem;
    animation: fadeIn 0.3s ease;
}

/* Next Question button inside feedback */
.challenge-feedback .btn-next {
    display: inline-block;
    margin-top: 1rem;
    padding: 0.65rem 1.5rem;
    background: var(--primary);
    color: #fff;
    border: none;
    border-radius: 0.5rem;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s, transform 0.15s;
}

.challenge-feedback .btn-next:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.challenge-difficulty {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
    margin-bottom: 1.25rem;
    flex-wrap: wrap;
}

.challenge-diff-btn {
    padding: 0.5rem 1.25rem;
    border-radius: 99px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    border: 2px solid var(--border-glass);
    background: var(--surface-glass);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-main);
    transition: all 0.3s;
}

.challenge-diff-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    transform: translateY(0);
    box-shadow: 0 2px 10px var(--primary-glow-subtle);
}

.challenge-diff-btn.active {
    background: linear-gradient(135deg, var(--primary), var(--primary-hover));
    color: #fff;
    border-color: var(--primary);
    box-shadow: 0 4px 16px var(--primary-glow);
}

/* NETWORK DIAGRAM */
.diagram-container {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--border-glass);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin-bottom: 2rem;
    text-align: center;
    overflow-x: auto;
    box-shadow: var(--glass-highlight);
}

.diagram-svg {
    width: 100%;
    height: auto;
    max-height: 750px;
}

.diagram-info-card {
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border-radius: var(--radius);
    box-shadow: var(--shadow-glow), var(--glass-highlight);
    padding: 2rem;
    margin-bottom: 2rem;
    border: 1px solid var(--border-glass);
}

@media (max-width: 768px) {
    .diagram-svg {
        max-height: 500px;
    }
    .diagram-container {
        padding: 0.75rem;
    }
}

/* SKIP LINK (Accessibility) */

.skip-link {
    position: absolute;
    left: -9999px;
    top: auto;
    width: 1px;
    height: 1px;
    overflow: hidden;
    z-index: 100;
    padding: 1rem 1.5rem;
    background: var(--primary);
    color: #fff;
    font-weight: 600;
    border-radius: 0 0 var(--radius) 0;
    text-decoration: none;
    font-size: 0.95rem;
}

.skip-link:focus {
    position: fixed;
    left: 0;
    top: 0;
    width: auto;
    height: auto;
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

/* FOCUS-VISIBLE (Accessibility) */
button:focus-visible,
input:focus-visible,
select:focus-visible,
a:focus-visible,
[tabindex]:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

/* Remove default outline only when we have :focus-visible support */
@supports selector(:focus-visible) {
    button:focus:not(:focus-visible),
    input:focus:not(:focus-visible),
    select:focus:not(:focus-visible),
    a:focus:not(:focus-visible) {
        outline: none;
    }
}

/* =============================================
   VLSM Calculator
   ============================================= */
.vlsm-subnets-builder {
    margin-top: 1.5rem;
    padding: 1.25rem;
    background: var(--primary-tint-light);
    border-radius: var(--radius);
    border: 1px solid var(--primary-tint-border);
}

.vlsm-subnets-builder h4 {
    margin: 0 0 0.25rem 0;
    color: var(--primary);
}

.vlsm-row {
    display: flex;
    gap: 0.75rem;
    align-items: center;
    margin-bottom: 0.5rem;
    animation: cellPopIn 0.25s ease-out both;
}

.vlsm-row .vlsm-name {
    flex: 2;
    padding: 0.6rem 0.75rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    background: var(--input-bg);
    color: var(--text-main);
    font-size: 0.9rem;
    transition: border-color 0.2s;
}

.vlsm-row .vlsm-hosts {
    flex: 1;
    padding: 0.6rem 0.75rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    background: var(--input-bg);
    color: var(--text-main);
    font-size: 0.9rem;
    transition: border-color 0.2s;
}

.vlsm-row .vlsm-name:focus,
.vlsm-row .vlsm-hosts:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-glow-subtle);
}

.vlsm-remove-btn {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--danger);
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: all 0.2s;
    line-height: 1;
    padding: 0;
}

.vlsm-remove-btn:hover {
    background: var(--danger-tint);
    border-color: var(--danger);
    transform: scale(1.1);
}

.vlsm-actions {
    display: flex;
    gap: 0.75rem;
    margin-top: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* =============================================
   Network Tools — Overlap & Summarization
   ============================================= */
.overlap-row {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
    align-items: flex-end;
}

.overlap-visual-bar {
    position: relative;
    /* height set dynamically via inline style */
    height: 48px;
    background: var(--neutral-tint);
    border-radius: 8px;
    margin-top: 0.5rem;
    overflow: visible;
    border: 1px solid var(--border);
}

.overlap-bar-segment {
    position: absolute;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0.82;
    transition: opacity 0.2s, transform 0.2s;
    cursor: pointer;
    min-width: 28px;
    box-sizing: border-box;
}

.overlap-bar-segment.overlap-bar-conflict {
    border: 3px dashed #fff;
    box-shadow: 0 0 0 2px var(--danger), inset 0 0 8px rgba(220,38,38,0.25);
    opacity: 0.92;
    animation: overlapPulse 1.8s ease-in-out infinite;
}

@keyframes overlapPulse {
    0%, 100% { box-shadow: 0 0 0 2px var(--danger), inset 0 0 8px rgba(220,38,38,0.25); }
    50%      { box-shadow: 0 0 0 4px var(--danger), inset 0 0 12px rgba(220,38,38,0.4); }
}

.overlap-bar-segment:hover {
    opacity: 1;
    z-index: 10;
    transform: scaleY(1.15);
}

.overlap-bar-segment span {
    color: #fff;
    font-size: 0.8rem;
    font-weight: 700;
    text-shadow: 0 1px 3px rgba(0,0,0,0.4);
    pointer-events: none;
}

.overlap-bar-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 10px 18px;
    margin-top: 8px;
    font-size: 0.82rem;
}

.overlap-legend-item {
    display: inline-flex;
    align-items: center;
    gap: 5px;
}

.overlap-legend-swatch {
    display: inline-block;
    width: 14px;
    height: 14px;
    border-radius: 4px;
    flex-shrink: 0;
}

/* =============================================
   Copy Results Button
   ============================================= */
.copy-result-wrap {
    position: relative;
}

.copy-result-btn {
    position: absolute;
    top: 0;
    right: 0;
    padding: 0.35rem 0.7rem;
    font-size: 0.78rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    background: var(--surface-glass);
    backdrop-filter: blur(var(--glass-blur));
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s;
    z-index: 5;
    white-space: nowrap;
}

.copy-result-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    background: var(--primary-tint-light);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.copy-result-btn.copied {
    border-color: var(--secondary);
    color: var(--secondary);
    background: var(--secondary-tint);
}

/* =============================================
   Challenge History
   ============================================= */
.challenge-history-section {
    border-top: 1px solid var(--border);
    margin-top: 1.5rem;
    padding-top: 0.5rem;
}

.challenge-history-grid {
    margin-top: 0.5rem;
}

@media (max-width: 600px) {
    .vlsm-row {
        flex-wrap: wrap;
    }
    .vlsm-row .vlsm-name,
    .vlsm-row .vlsm-hosts {
        flex: 1 1 100%;
    }
    .overlap-row {
        flex-wrap: wrap;
    }
    .overlap-row .calc-input-group {
        flex: 1 1 100% !important;
    }
    .vlsm-actions {
        flex-direction: column;
        align-items: stretch;
    }
    .copy-result-btn {
        position: relative;
        display: block;
        margin-bottom: 0.75rem;
        text-align: center;
    }
}