/**
 * CSE220 Array Extensions — Section-Based Layout
 * Design System: Uses global CSS variables from _variables.css
 * Pattern: Full-width paper-card sections with educational content + interactive visualizers
 */

/* ==========================================================================
   1. CONTAINER & SECTION DIVIDER
   ========================================================================== */

#cse220-array-extensions {
    margin-top: 3rem;
    padding-top: 2rem;
    position: relative;
}

/* Decorative section divider */
#cse220-array-extensions::before {
    content: "";
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80%;
    height: 1px;
    background: linear-gradient(
        90deg,
        transparent 0%,
        var(--border-soft) 20%,
        var(--accent-forest) 50%,
        var(--border-soft) 80%,
        transparent 100%
    );
}

/* Intro header */
.cse220-intro {
    text-align: center;
    margin-bottom: 2.5rem;
    animation: cse220FadeIn 0.6s ease-out;
}

.cse220-intro h2 {
    font-size: 1.6rem;
    font-weight: 800;
    color: var(--text-dark);
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.cse220-intro .subtitle {
    font-size: 0.95rem;
    color: var(--text-muted);
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.6;
}

@keyframes cse220FadeIn {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ==========================================================================
   2. SECTION CARDS
   ========================================================================== */

.cse220-section {
    background: var(--bg-card);
    border: 1px solid var(--border-soft);
    border-radius: 16px;
    padding: 2rem;
    margin-bottom: 2rem;
    position: relative;
    overflow: hidden;
    box-shadow:
        0 2px 12px var(--shadow-warm),
        0 8px 24px var(--shadow-warm);
    transition:
        background var(--theme-transition),
        border-color var(--theme-transition),
        box-shadow 0.3s ease;
}

/* Top accent bar — same as paper-card */
.cse220-section::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg,
        var(--section-accent, var(--accent-forest)),
        var(--accent-sage),
        var(--accent-amber));
    opacity: 0.7;
}

/* Accent variants */
.cse220-section[data-accent="manipulations"]::before {
    background: linear-gradient(90deg, #3b82f6, #60a5fa, #93c5fd);
}

.cse220-section[data-accent="search"]::before {
    background: linear-gradient(90deg, #10b981, #34d399, #6ee7b7);
}

.cse220-section[data-accent="2d"]::before {
    background: linear-gradient(90deg, #ec4899, #f472b6, #f9a8d4);
}

.cse220-section[data-accent="exam"]::before {
    background: linear-gradient(90deg, #8b5cf6, #a78bfa, #c4b5fd);
}

/* ==========================================================================
   3. SECTION HEADERS
   ========================================================================== */

.cse220-section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.cse220-section-header .header-left {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.cse220-section-header h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-dark);
    margin: 0;
    letter-spacing: -0.01em;
}

.cse220-badge {
    display: inline-flex;
    align-items: center;
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: white;
}

.cse220-badge.badge-course {
    background: var(--accent-forest);
}

.cse220-badge.badge-critical {
    background: var(--accent-coral);
}

.cse220-badge.badge-prep {
    background: var(--accent-plum);
}

/* ==========================================================================
   4. EDUCATIONAL CONTENT
   ========================================================================== */

.cse220-content {
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

.cse220-content p {
    color: var(--text-body);
    font-size: 0.95rem;
    margin-bottom: 1rem;
}

.cse220-content strong {
    color: var(--text-dark);
}

/* Concept Grid — side by side explanations */
.concept-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1rem;
    margin: 1.25rem 0;
}

.concept-card {
    background: var(--viz-bg-subtle);
    border: 1px solid var(--border-soft);
    border-radius: 12px;
    padding: 1.25rem;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.concept-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow-warm);
}

.concept-card h4 {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-dark);
    margin: 0 0 0.5rem 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.concept-card .concept-icon {
    width: 28px;
    height: 28px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.85rem;
    color: white;
    flex-shrink: 0;
}

.concept-card p {
    font-size: 0.88rem;
    color: var(--text-muted);
    margin: 0;
    line-height: 1.5;
}

/* Pseudocode blocks */
.pseudocode-block {
    background: var(--viz-bg-code);
    border-left: 3px solid var(--accent-forest);
    border-radius: 0 8px 8px 0;
    padding: 1rem 1.25rem;
    margin: 1rem 0;
    font-family: 'JetBrains Mono', 'Fira Code', monospace;
    font-size: 0.82rem;
    line-height: 1.6;
    color: var(--text-body);
    overflow-x: auto;
}

[data-theme="dark"] .pseudocode-block {
    background: rgba(0, 0, 0, 0.3);
    border-left-color: var(--accent-sage);
    color: #e2e8f0;
}

/* Exam tip callout */
.exam-tip {
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.05), rgba(139, 92, 246, 0.02));
    border: 1px solid rgba(139, 92, 246, 0.15);
    border-left: 4px solid #8b5cf6;
    border-radius: 0 12px 12px 0;
    padding: 1rem 1.25rem;
    margin: 1.25rem 0;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
}

[data-theme="dark"] .exam-tip {
    background: linear-gradient(135deg, rgba(139, 92, 246, 0.12), rgba(139, 92, 246, 0.05));
    border-color: rgba(139, 92, 246, 0.25);
}

.exam-tip .tip-icon {
    font-size: 1.2rem;
    flex-shrink: 0;
    margin-top: 2px;
}

.exam-tip .tip-content {
    font-size: 0.88rem;
    color: var(--text-body);
    line-height: 1.5;
}

.exam-tip .tip-content strong {
    color: #8b5cf6;
}

[data-theme="dark"] .exam-tip .tip-content strong {
    color: #a78bfa;
}

/* Key insight callout */
.key-insight {
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.05), rgba(16, 185, 129, 0.02));
    border: 1px solid rgba(16, 185, 129, 0.15);
    border-left: 4px solid #10b981;
    border-radius: 0 12px 12px 0;
    padding: 1rem 1.25rem;
    margin: 1.25rem 0;
}

[data-theme="dark"] .key-insight {
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.12), rgba(16, 185, 129, 0.05));
    border-color: rgba(16, 185, 129, 0.25);
}

.key-insight p {
    font-size: 0.88rem;
    color: var(--text-body);
    margin: 0;
}

.key-insight strong {
    color: #10b981;
}

[data-theme="dark"] .key-insight strong {
    color: #34d399;
}

/* ==========================================================================
   5. INTERACTIVE AREA (SPLIT LAYOUT)
   ========================================================================== */

.cse220-interactive {
    background: var(--viz-bg-subtle);
    border: 1px solid var(--border-soft);
    border-radius: 12px;
    padding: 1.5rem;
    margin-top: 1rem;
}

/* The Grid System - 60% Canvas / 40% Code */
.viz-split-layout {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 1.5rem;
    margin-top: 1rem;
    align-items: start;
}

/* Left Column: Canvas */
.viz-canvas-column {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    min-width: 0; /* Critical for grid resizing */
}

/* Right Column: Code Editor */
.viz-code-column {
    background: #1e1e2e; /* Editor BG - matches OneDark */
    border: 1px solid var(--border-soft);
    border-radius: 12px;
    overflow: hidden;
    height: 100%;
    min-height: 480px; /* Match typical canvas height */
    display: flex;
    flex-direction: column;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.2);
}

[data-theme="dark"] .viz-code-column {
    border-color: rgba(255,255,255,0.1);
}

.viz-code-header {
    background: #252535;
    padding: 0.6rem 1rem;
    border-bottom: 1px solid rgba(255,255,255,0.05);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.code-lang-badge {
    font-size: 0.7rem;
    font-weight: 700;
    color: #a9b1d6;
    background: rgba(255,255,255,0.1);
    padding: 2px 6px;
    border-radius: 4px;
    letter-spacing: 0.05em;
}

.code-title {
    font-size: 0.8rem;
    color: #7aa2f7; /* Soft Blue */
    font-family: 'JetBrains Mono', monospace;
    font-weight: 600;
}

.viz-code-editor-container {
    flex: 1;
    overflow: hidden;
    position: relative;
    font-size: 13px;
}

/* Controls Area (Full Width above Grid) */
.cse220-controls-area {
    margin-bottom: 1rem;
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    align-items: center;
    justify-content: space-between;
}

/* Responsive: Stack on smaller screens */
@media (max-width: 1100px) {
    .viz-split-layout {
        grid-template-columns: 1fr;
    }
    
    .viz-code-column {
        min-height: 350px;
        max-height: 500px;
    }
}


/* Custom Input Row */
.cse220-input-row {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.cse220-input-row label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
    white-space: nowrap;
}

.cse220-input {
    flex: 1;
    min-width: 180px;
    padding: 0.5rem 0.75rem;
    background: var(--bg-card);
    border: 1px solid var(--border-soft);
    border-radius: 8px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    color: var(--text-dark);
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.cse220-input:focus {
    outline: none;
    border-color: var(--accent-forest);
    box-shadow: 0 0 0 3px var(--focus-ring);
}

.cse220-input::placeholder {
    color: var(--text-muted);
    opacity: 0.6;
}

/* Light mode input fix */
:root:not([data-theme="dark"]) .cse220-input {
    background: #ffffff;
    border-color: #d4d4d8;
    color: #18181b;
}

:root:not([data-theme="dark"]) .cse220-input::placeholder {
    color: #a1a1aa;
}

/* Small number input */
.cse220-input-sm {
    width: 60px;
    min-width: 60px;
    flex: 0;
    text-align: center;
}

/* Button Row */
.cse220-btn-row {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-bottom: 1rem;
}

.cse220-btn {
    padding: 0.4rem 0.85rem;
    border-radius: 8px;
    font-size: 0.8rem;
    font-weight: 600;
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
}

.cse220-btn:active {
    transform: scale(0.97);
}

.cse220-btn-primary {
    background: linear-gradient(180deg, rgba(255,255,255,0.15) 0%, rgba(255,255,255,0) 100%),
        var(--accent-forest);
    color: white;
    border: 1px solid rgba(255,255,255,0.2);
    box-shadow: 0 2px 8px rgba(0,0,0,0.15), inset 0 1px 0 rgba(255,255,255,0.2);
}

.cse220-btn-primary:hover {
    filter: brightness(1.1);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.2);
}

.cse220-btn-secondary {
    background: var(--viz-bg-subtle);
    color: var(--text-body);
    border: 1px solid var(--border-soft);
}

.cse220-btn-secondary:hover {
    background: var(--viz-bg-element);
    border-color: var(--text-muted);
}

.cse220-btn-accent {
    background: linear-gradient(180deg, rgba(255,255,255,0.15) 0%, rgba(255,255,255,0) 100%),
        var(--accent-coral);
    color: white;
    border: 1px solid rgba(255,255,255,0.2);
    box-shadow: 0 2px 8px rgba(0,0,0,0.15), inset 0 1px 0 rgba(255,255,255,0.2);
}

.cse220-btn-accent:hover {
    filter: brightness(1.1);
    transform: translateY(-1px);
}

.cse220-btn-ghost {
    background: transparent;
    color: var(--text-muted);
    border: 1px solid var(--border-soft);
}

.cse220-btn-ghost:hover {
    background: var(--viz-bg-subtle);
    color: var(--text-dark);
}

.cse220-btn-toggle {
    background: var(--viz-bg-element);
    color: var(--text-dark);
    border: 1px solid var(--border-soft);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
}

.cse220-btn-toggle.active {
    background: var(--accent-forest);
    color: white;
    border-color: var(--accent-forest);
}

/* Canvas Container */
.cse220-canvas-wrap {
    background: var(--bg-paper);
    border: 1px solid var(--border-soft);
    border-radius: 12px;
    padding: 0.75rem;
    margin-bottom: 0.75rem;
    overflow: hidden;
}

[data-theme="dark"] .cse220-canvas-wrap {
    background: rgba(0, 0, 0, 0.2);
    border-color: rgba(255, 255, 255, 0.08);
}

.cse220-canvas-wrap canvas {
    width: 100%;
    display: block;
    border-radius: 8px;
}

/* Status bar */
.cse220-status {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 0.75rem;
    background: var(--viz-bg-code);
    border-radius: 6px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    color: var(--accent-forest);
    min-height: 32px;
}

[data-theme="dark"] .cse220-status {
    background: rgba(0, 0, 0, 0.3);
    color: var(--accent-sage);
}

.cse220-status .status-dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-forest);
    flex-shrink: 0;
}

/* ==========================================================================
   6. COMPLEXITY TABLE
   ========================================================================== */

.cse220-table-wrap {
    background: var(--bg-paper);
    border: 1px solid var(--border-soft);
    border-radius: 12px;
    overflow: hidden;
    margin: 1rem 0;
}

.cse220-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.88rem;
}

.cse220-table thead {
    background: var(--viz-bg-subtle);
}

.cse220-table th {
    padding: 0.75rem 1rem;
    text-align: left;
    font-weight: 700;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-muted);
    border-bottom: 2px solid var(--border-soft);
}

.cse220-table td {
    padding: 0.65rem 1rem;
    color: var(--text-body);
    border-bottom: 1px solid var(--border-soft);
}

.cse220-table tbody tr:last-child td {
    border-bottom: none;
}

.cse220-table tbody tr:hover {
    background: var(--viz-bg-subtle);
}

/* Complexity badges in table */
.complexity-pill {
    display: inline-flex;
    padding: 2px 8px;
    border-radius: 12px;
    font-size: 0.78rem;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
}

.complexity-pill.fast {
    background: rgba(16, 185, 129, 0.12);
    color: #10b981;
}

.complexity-pill.medium {
    background: rgba(245, 158, 11, 0.12);
    color: #f59e0b;
}

.complexity-pill.slow {
    background: rgba(239, 68, 68, 0.12);
    color: #ef4444;
}

[data-theme="dark"] .complexity-pill.fast {
    background: rgba(16, 185, 129, 0.2);
    color: #6ee7b7;
}

[data-theme="dark"] .complexity-pill.medium {
    background: rgba(245, 158, 11, 0.2);
    color: #fcd34d;
}

[data-theme="dark"] .complexity-pill.slow {
    background: rgba(239, 68, 68, 0.2);
    color: #fca5a5;
}

/* ==========================================================================
   7. 2D MODULE SPECIFIC
   ========================================================================== */

.cse220-formula-bar {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.6rem 1rem;
    background: var(--viz-bg-code);
    border-radius: 8px;
    margin-top: 0.75rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    color: var(--accent-forest);
    border-left: 3px solid var(--accent-coral);
}

[data-theme="dark"] .cse220-formula-bar {
    background: rgba(0, 0, 0, 0.3);
    color: var(--accent-sage);
}

/* ---------- 2D Interactive Panel ---------- */

#viz-2d-ops-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-soft);
    border-radius: 16px;
    overflow: hidden;
    box-shadow:
        0 2px 12px var(--shadow-warm),
        0 8px 24px var(--shadow-warm);
    position: relative;
}

/* Top accent bar */
#viz-2d-ops-panel::before {
    content: "";
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: linear-gradient(90deg, #ec4899, #f472b6, #f9a8d4);
    opacity: 0.8;
    z-index: 1;
}

/* Header area */
.viz-2d-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-soft);
    background: var(--viz-bg-subtle);
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.viz-2d-header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.viz-2d-header h4 {
    margin: 0;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-dark);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Grid size controls */
.viz-2d-grid-controls {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--bg-card);
    padding: 6px 12px;
    border-radius: 10px;
    border: 1px solid var(--border-soft);
}

.viz-2d-grid-controls .grid-label {
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.viz-2d-grid-controls input[type="number"] {
    width: 42px;
    padding: 4px 6px;
    border: 1px solid var(--border-soft);
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    text-align: center;
    background: var(--bg-paper);
    color: var(--text-dark);
    font-family: 'JetBrains Mono', monospace;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.viz-2d-grid-controls input[type="number"]:focus {
    outline: none;
    border-color: var(--accent-forest);
    box-shadow: 0 0 0 3px var(--focus-ring);
}

.viz-2d-grid-controls .grid-separator {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-weight: 600;
}

/* ---- Operation Button Pills ---- */
.viz-2d-ops-row {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.viz-2d-op-btn {
    padding: 0.4rem 0.85rem;
    border-radius: 20px;
    font-size: 0.78rem;
    font-weight: 600;
    border: 1px solid var(--border-soft);
    background: var(--bg-card);
    color: var(--text-body);
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    white-space: nowrap;
}

.viz-2d-op-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px var(--shadow-warm);
    border-color: var(--text-muted);
    color: var(--text-dark);
}

.viz-2d-op-btn:active {
    transform: scale(0.97);
}

.viz-2d-op-btn.active {
    color: white;
    border-color: transparent;
    box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

/* Category Colors for Active State */
.viz-2d-op-btn[data-cat="traverse"].active {
    background: linear-gradient(135deg, #3b82f6, #60a5fa);
}
.viz-2d-op-btn[data-cat="arithmetic"].active {
    background: linear-gradient(135deg, #10b981, #34d399);
}
.viz-2d-op-btn[data-cat="structural"].active {
    background: linear-gradient(135deg, #ef4444, #f87171);
}
.viz-2d-op-btn[data-cat="diagonal"].active {
    background: linear-gradient(135deg, #8b5cf6, #a78bfa);
}
.viz-2d-op-btn[data-cat="matrix"].active {
    background: linear-gradient(135deg, #f59e0b, #fbbf24);
}

/* ---- Icon Buttons (Playback) ---- */
.cse220-icon-btn {
    width: 36px;
    height: 36px;
    border-radius: 10px;
    border: 1px solid var(--border-soft);
    background: var(--bg-card);
    color: var(--text-muted);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.cse220-icon-btn:hover:not(:disabled) {
    background: var(--viz-bg-element);
    color: var(--text-dark);
    transform: scale(1.08);
    box-shadow: 0 2px 8px var(--shadow-warm);
}

.cse220-icon-btn:disabled {
    opacity: 0.35;
    cursor: not-allowed;
}

.cse220-icon-btn.primary {
    width: 44px;
    height: 44px;
    border-radius: 14px;
    background: #3b82f6;
    color: white;
    border: none;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.cse220-icon-btn.primary:hover:not(:disabled) {
    background: #2563eb;
    transform: scale(1.08);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.4);
}

/* ---- Code Editor ---- */
.viz-code-editor {
    flex: 1;
    overflow-y: auto;
    padding: 1rem;
    font-family: 'JetBrains Mono', 'Fira Code', monospace;
    font-size: 0.82rem;
    line-height: 1.7;
    color: #a9b1d6;
    counter-reset: line;
    min-height: 240px;
}

.viz-code-line {
    padding: 2px 8px 2px 12px;
    border-left: 3px solid transparent;
    border-radius: 0 4px 4px 0;
    transition: all 0.2s ease;
    position: relative;
    counter-increment: line;
}

.viz-code-line::before {
    content: counter(line);
    position: absolute;
    left: -28px;
    width: 20px;
    text-align: right;
    font-size: 0.7rem;
    color: rgba(255,255,255,0.15);
    font-weight: 500;
}

.viz-code-line.active {
    background: rgba(59, 130, 246, 0.12);
    border-left-color: #3b82f6;
    color: #e2e8f0;
}

/* Scrollbar for code editor */
.viz-code-editor::-webkit-scrollbar {
    width: 6px;
}
.viz-code-editor::-webkit-scrollbar-track {
    background: transparent;
}
.viz-code-editor::-webkit-scrollbar-thumb {
    background: rgba(255,255,255,0.1);
    border-radius: 3px;
}

/* ---- Variable Inspector (2D) ---- */
.viz-var-inspector {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(70px, 1fr));
    gap: 0.5rem;
    padding: 0.75rem;
    background: var(--bg-paper);
    border: 1px solid var(--border-soft);
    border-radius: 10px;
    margin-top: 0.5rem;
}

.viz-var-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    background: var(--bg-card);
    padding: 0.4rem 0.6rem;
    border-radius: 8px;
    border: 1px solid var(--border-soft);
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.viz-var-item span:first-child {
    font-size: 0.7rem;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    text-transform: none;
}

.viz-var-item span:last-child {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-dark);
    font-family: 'JetBrains Mono', monospace;
}

/* Highlight when value changes */
.viz-var-item.flash {
    border-color: var(--accent-sky);
    box-shadow: 0 0 8px rgba(59, 130, 246, 0.2);
}

/* ---- Playback Bar ---- */
.viz-playback-controls {
    display: flex;
    gap: 10px;
    align-items: center;
    justify-content: center;
    background: var(--viz-bg-code);
    padding: 10px 16px;
    border-radius: 12px;
    border: 1px solid var(--border-soft);
    margin-top: 0.5rem;
}

.viz-playback-controls .viz-divider {
    width: 1px;
    height: 24px;
    background: var(--border-soft);
    margin: 0 4px;
}

.viz-speed-group {
    display: flex;
    align-items: center;
    gap: 6px;
}

.viz-speed-group .speed-label {
    font-size: 0.7rem;
    color: var(--text-muted);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.viz-speed-group input[type="range"] {
    width: 60px;
    accent-color: var(--accent-sky);
}

.viz-speed-group .speed-value {
    font-size: 0.75rem;
    color: var(--text-dark);
    font-weight: 700;
    min-width: 24px;
    font-family: 'JetBrains Mono', monospace;
}

/* ---- Step Progress Badge ---- */
.viz-step-badge {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-muted);
    font-family: 'JetBrains Mono', monospace;
    padding: 2px 8px;
    background: var(--bg-card);
    border-radius: 6px;
    border: 1px solid var(--border-soft);
}

/* ---- 2D Panel Body ---- */
.viz-2d-body {
    padding: 1.25rem;
}

/* ---- Animations / Effects ---- */
@keyframes cellPulse {
    0%  { transform: scale(1);    opacity: 0.7; }
    50% { transform: scale(1.08); opacity: 1; }
    100%{ transform: scale(1);    opacity: 0.7; }
}
@keyframes codeLineFlash {
    0%  { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100%{ background-position: 0% 50%; }
}
@keyframes varFlash {
    0%   { background: transparent; }
    30%  { background: rgba(99, 102, 241, 0.15); }
    100% { background: transparent; }
}
@keyframes resultGlow {
    0%   { box-shadow: 0 0 0 0 rgba(52, 211, 153, 0.5); }
    70%  { box-shadow: 0 0 8px 4px rgba(52, 211, 153, 0.25); }
    100% { box-shadow: 0 0 0 0 rgba(52, 211, 153, 0); }
}
@keyframes btnActiveGlow {
    0%   { box-shadow: 0 0 0 0 var(--accent-primary, #6366f1); }
    50%  { box-shadow: 0 0 12px 3px var(--accent-primary, #6366f1); }
    100% { box-shadow: 0 0 0 0 var(--accent-primary, #6366f1); }
}

/* Active code line gets a shimmer effect */
.viz-code-line.active {
    animation: codeLineFlash 2s ease infinite;
    background-size: 200% 200%;
}

/* Variable inspector flash on value change */
.viz-var-item.flash {
    animation: varFlash 0.4s ease-out;
}

/* Active operation button subtle glow */
.viz-2d-op-btn.active {
    animation: btnActiveGlow 1.5s ease infinite;
}

/* ---- Responsive ---- */
@media (max-width: 1100px) {
    .viz-2d-ops-row {
        gap: 4px;
    }
    .viz-2d-op-btn {
        font-size: 0.72rem;
        padding: 0.35rem 0.65rem;
    }
}

@media (max-width: 768px) {
    .viz-2d-header {
        padding: 1rem;
    }
    .viz-2d-header-row {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.75rem;
    }
    .viz-2d-ops-row {
        gap: 4px;
    }
    .viz-2d-op-btn {
        font-size: 0.7rem;
        padding: 0.3rem 0.55rem;
    }
}

/* ==========================================================================
   8. RESPONSIVE
   ========================================================================== */

@media (max-width: 768px) {
    .cse220-section {
        padding: 1.25rem;
        margin-bottom: 1.5rem;
    }

    .cse220-section-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .concept-grid {
        grid-template-columns: 1fr;
    }

    .cse220-input-row {
        flex-direction: column;
        align-items: stretch;
    }

    .cse220-input {
        min-width: auto;
    }

    .cse220-btn-row {
        gap: 0.35rem;
    }

    .cse220-btn {
        font-size: 0.75rem;
        padding: 0.35rem 0.65rem;
    }

    .cse220-intro h2 {
        font-size: 1.3rem;
    }
}

@media (max-width: 480px) {
    .cse220-section {
        padding: 1rem;
        border-radius: 12px;
    }

    .cse220-interactive {
        padding: 1rem;
    }
}