/* ═══════════════════════════════════════════════════════════════════════════
   VisualizedSorting — Custom Design System
   Phase 1: UI Shell
   ═══════════════════════════════════════════════════════════════════════════ */

/* ─── RESET ─────────────────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
button, input { font-family: inherit; }

/* ─── DESIGN TOKENS ──────────────────────────────────────────────────────────── */
:root {
    --vs-bg:            #08080f;
    --vs-surface:       #0f0f1e;
    --vs-card:          #16162a;
    --vs-card-hover:    #1c1c38;
    --vs-border:        #252545;
    --vs-border-light:  #2e2e55;

    --vs-blue:          #5b8af7;
    --vs-violet:        #8b5cf6;
    --vs-gradient:      linear-gradient(135deg, #5b8af7 0%, #8b5cf6 100%);
    --vs-gradient-sub:  linear-gradient(135deg, rgba(91,138,247,.12) 0%, rgba(139,92,246,.12) 100%);
    --vs-glow-blue:     rgba(91,138,247,.3);

    --vs-text:          #e8e8f5;
    --vs-text-2:        #9898bb;
    --vs-text-3:        #555570;

    --vs-bar-default:   #3d3d6e;
    --vs-bar-compare:   #f5c842;
    --vs-bar-swap:      #f05454;
    --vs-bar-sorted:    #42d97a;

    --vs-font:          'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --vs-mono:          'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

    --vs-radius:        12px;
    --vs-radius-sm:     8px;
    --vs-radius-xs:     6px;
}

/* ─── BASE ───────────────────────────────────────────────────────────────────── */
html {
    font-family: var(--vs-font);
    background: var(--vs-bg);
    color: var(--vs-text);
    scroll-behavior: smooth;
    font-size: 16px;
}
body { min-height: 100vh; overflow-x: hidden; }

::-webkit-scrollbar { width: 5px; }
::-webkit-scrollbar-track { background: var(--vs-bg); }
::-webkit-scrollbar-thumb { background: var(--vs-border-light); border-radius: 3px; }

/* ─── UTILITY ────────────────────────────────────────────────────────────────── */
.vs-container { max-width: 1280px; margin: 0 auto; padding: 0 2rem; }
.vs-hidden    { display: none !important; }

.vs-gradient-text {
    background: var(--vs-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ─── EYEBROW ────────────────────────────────────────────────────────────────── */
.vs-eyebrow {
    display: inline-flex;
    align-items: center;
    gap: .5rem;
    font-size: .7rem;
    font-weight: 600;
    letter-spacing: .14em;
    color: var(--vs-blue);
    margin-bottom: 1.25rem;
}
.vs-eyebrow-dot {
    width: 6px; height: 6px;
    background: var(--vs-blue);
    border-radius: 50%;
    box-shadow: 0 0 8px var(--vs-blue);
    animation: vs-dot-pulse 2.2s ease-in-out infinite;
}
@keyframes vs-dot-pulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50%       { opacity: .4; transform: scale(.65); }
}

/* ─── NAVBAR ─────────────────────────────────────────────────────────────────── */
.vs-nav {
    position: sticky; top: 0; z-index: 200;
    background: rgba(8, 8, 15, .88);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--vs-border);
}
.vs-nav-inner {
    max-width: 1280px; margin: 0 auto;
    padding: 0 2rem; height: 64px;
    display: flex; align-items: center; justify-content: space-between;
}
.vs-nav-logo {
    font-size: 1.05rem; font-weight: 700;
    letter-spacing: -.025em; color: var(--vs-text);
    text-decoration: none;
}
.logo-bracket {
    background: var(--vs-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.vs-nav-links { display: flex; align-items: center; gap: 2rem; }
.vs-nav-link {
    color: var(--vs-text-2); text-decoration: none;
    font-size: .875rem; font-weight: 500;
    transition: color .2s;
}
.vs-nav-link:hover { color: var(--vs-text); }
.vs-nav-cta {
    background: var(--vs-gradient); color: #fff;
    text-decoration: none; font-size: .825rem; font-weight: 600;
    padding: .5rem 1.2rem; border-radius: var(--vs-radius-xs);
    transition: opacity .2s, transform .2s;
}
.vs-nav-cta:hover { opacity: .85; transform: translateY(-1px); }

/* ─── HERO ───────────────────────────────────────────────────────────────────── */
.vs-hero {
    position: relative;
    min-height: calc(100vh - 64px);
    display: flex; align-items: center;
    overflow: hidden;
}
.vs-hero-grid-bg {
    position: absolute; inset: 0;
    pointer-events: none; z-index: 0;
    background-image:
        linear-gradient(rgba(91,138,247,.045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(91,138,247,.045) 1px, transparent 1px);
    background-size: 56px 56px;
    mask-image: radial-gradient(ellipse 90% 85% at 50% 40%, black 20%, transparent 80%);
    -webkit-mask-image: radial-gradient(ellipse 90% 85% at 50% 40%, black 20%, transparent 80%);
}
.vs-hero-inner {
    position: relative; z-index: 1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem; align-items: center;
    padding: 5rem 0;
}

/* Hero text */
.vs-hero-title {
    font-size: clamp(2.8rem, 4.8vw, 4.6rem);
    font-weight: 900; line-height: 1.04;
    letter-spacing: -.045em;
    color: var(--vs-text); margin-bottom: 1.5rem;
}
.vs-hero-subtitle {
    font-size: 1.075rem; font-weight: 400; line-height: 1.75;
    color: var(--vs-text-2); margin-bottom: 2.5rem;
}
.vs-hero-actions { display: flex; flex-direction: column; gap: 2rem; }

.vs-btn-primary {
    display: inline-flex; align-items: center; gap: .5rem;
    background: var(--vs-gradient); color: #fff;
    text-decoration: none; font-size: .95rem; font-weight: 600;
    padding: .875rem 2rem; border-radius: var(--vs-radius-sm);
    width: fit-content;
    box-shadow: 0 4px 28px var(--vs-glow-blue);
    transition: transform .2s, box-shadow .2s;
}
.vs-btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 36px var(--vs-glow-blue);
}

.vs-hero-stats { display: flex; align-items: center; gap: 1.75rem; }
.vs-stat { display: flex; flex-direction: column; gap: .1rem; }
.vs-stat-num {
    font-size: 1.6rem; font-weight: 800;
    color: var(--vs-text); line-height: 1;
}
.vs-stat-label {
    font-size: .68rem; font-weight: 600; text-transform: uppercase;
    letter-spacing: .1em; color: var(--vs-text-3);
}
.vs-stat-divider { width: 1px; height: 2.2rem; background: var(--vs-border); }

/* Hero visual widget */
.vs-hero-visual {
    background: var(--vs-surface);
    border: 1px solid var(--vs-border);
    border-radius: 16px; padding: 1.25rem;
    position: relative; overflow: hidden;
    transition: border-color .3s;
}
.vs-hero-visual:hover { border-color: rgba(91,138,247,.45); }

.vs-hero-visual::after {
    content: '';
    position: absolute; inset: 0; border-radius: 16px;
    background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(91,138,247,.07), transparent 70%);
    pointer-events: none;
}

.vs-hero-visual-topbar {
    display: flex; align-items: center; justify-content: space-between;
    padding-bottom: .875rem;
    border-bottom: 1px solid var(--vs-border);
    margin-bottom: .875rem;
}
.vs-hero-visual-label {
    font-family: var(--vs-mono); font-size: .72rem;
    color: var(--vs-text-3);
}
.vs-hero-visual-status {
    font-size: .68rem; font-weight: 600; letter-spacing: .06em;
    color: var(--vs-bar-compare);
    animation: vs-status-blink 1.4s ease-in-out infinite;
}
@keyframes vs-status-blink {
    0%, 100% { opacity: 1; }
    50%       { opacity: .3; }
}

.vs-hero-bars-wrap {
    display: flex; align-items: flex-end;
    height: 190px; padding: 0 .25rem;
}
.vs-hero-bars {
    display: flex; align-items: flex-end;
    gap: 4px; width: 100%; height: 100%;
}

/* Individual hero bars */
.vs-hero-bar {
    flex: 1; min-width: 0;
    border-radius: 3px 3px 0 0;
    transform-origin: bottom;
    animation: vs-bar-dance var(--dur, 2s) var(--delay, 0s) ease-in-out infinite alternate;
}
@keyframes vs-bar-dance {
    from { transform: scaleY(1); }
    to   { transform: scaleY(var(--to, .45)); }
}
.vs-bar-default { background: var(--vs-bar-default); }
.vs-bar-compare { background: var(--vs-bar-compare); box-shadow: 0 0 10px rgba(245,200,66,.55); }
.vs-bar-swap    { background: var(--vs-bar-swap);    box-shadow: 0 0 10px rgba(240,84,84,.5); }
.vs-bar-sorted  { background: linear-gradient(180deg, #42d97a 0%, #2ab862 100%); box-shadow: 0 0 8px rgba(66,217,122,.3); }

/* Legend */
.vs-hero-visual-legend {
    display: flex; align-items: center; gap: 1.1rem;
    flex-wrap: wrap;
    padding-top: .875rem;
    border-top: 1px solid var(--vs-border);
    margin-top: .875rem;
}
.vs-legend-item {
    display: inline-flex; align-items: center; gap: .3rem;
    font-size: .7rem; color: var(--vs-text-3);
}
.vs-legend-dot {
    width: 8px; height: 8px; border-radius: 2px; flex-shrink: 0;
}
.vs-dot-default { background: var(--vs-bar-default); }
.vs-dot-compare { background: var(--vs-bar-compare); }
.vs-dot-swap    { background: var(--vs-bar-swap); }
.vs-dot-sorted  { background: var(--vs-bar-sorted); }

/* ─── ALGORITHMS SECTION ─────────────────────────────────────────────────────── */
.vs-algos-section { padding: 6rem 0; }

.vs-section-header { text-align: center; margin-bottom: 4rem; }
.vs-section-title {
    font-size: clamp(1.9rem, 3vw, 2.6rem);
    font-weight: 800; letter-spacing: -.035em;
    margin-bottom: .875rem; margin-top: .75rem;
}
.vs-section-subtitle {
    font-size: 1rem; line-height: 1.75;
    color: var(--vs-text-2);
    max-width: 540px; margin: 0 auto;
}

/* Algorithm card grid */
.vs-algo-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.25rem;
}

.vs-algo-card {
    background: var(--vs-card);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius);
    padding: 1.75rem;
    cursor: pointer; position: relative; overflow: hidden;
    transition: transform .25s, background .25s, border-color .25s, box-shadow .25s;
}
.vs-algo-card::before {
    content: '';
    position: absolute; inset: 0;
    background: var(--vs-gradient-sub);
    opacity: 0; transition: opacity .25s;
    border-radius: var(--vs-radius);
}
.vs-algo-card:hover {
    transform: translateY(-5px);
    background: var(--vs-card-hover);
    border-color: rgba(91,138,247,.55);
    box-shadow: 0 10px 44px rgba(91,138,247,.12);
}
.vs-algo-card:hover::before { opacity: 1; }

.vs-algo-card-header {
    display: flex; align-items: flex-start;
    justify-content: space-between; gap: .75rem;
    margin-bottom: 1.25rem;
}
.vs-algo-name {
    font-size: 1.075rem; font-weight: 700;
    letter-spacing: -.02em; line-height: 1.2;
}

/* Category badges */
.vs-category-badge {
    font-size: .62rem; font-weight: 600; letter-spacing: .08em;
    text-transform: uppercase; padding: .25rem .65rem;
    border-radius: 20px; white-space: nowrap; flex-shrink: 0;
}
.vs-badge-comparison {
    background: rgba(91,138,247,.13); color: var(--vs-blue);
    border: 1px solid rgba(91,138,247,.3);
}
.vs-badge-noncomparison {
    background: rgba(139,92,246,.13); color: var(--vs-violet);
    border: 1px solid rgba(139,92,246,.3);
}

/* Complexity table */
.vs-complexity-table {
    width: 100%; border-collapse: collapse;
    margin-bottom: 1.25rem;
}
.vs-complexity-table td {
    padding: .375rem 0; font-size: .8rem;
    border-bottom: 1px solid rgba(255,255,255,.04);
}
.vs-complexity-table tr:last-child td { border-bottom: none; }
.vs-complexity-table td:first-child {
    color: var(--vs-text-3); font-weight: 500; width: 55%;
}
.vs-complexity-table td:last-child {
    font-family: var(--vs-mono); font-size: .77rem;
    font-weight: 500; color: var(--vs-text);
}

.vs-card-footer {
    display: flex; align-items: center;
    justify-content: flex-end; gap: .35rem;
    font-size: .8rem; font-weight: 600; color: var(--vs-blue);
    opacity: 0; transform: translateX(-6px);
    transition: opacity .25s, transform .25s;
}
.vs-algo-card:hover .vs-card-footer { opacity: 1; transform: translateX(0); }

/* ─── VISUALIZER SECTION ─────────────────────────────────────────────────────── */
.vs-viz-section { padding: 2rem 0 6rem; }

.vs-back-btn {
    display: inline-flex; align-items: center; gap: .5rem;
    background: transparent;
    border: 1px solid var(--vs-border);
    color: var(--vs-text-2); font-size: .85rem; font-weight: 500;
    padding: .5rem 1.1rem; border-radius: var(--vs-radius-xs);
    cursor: pointer; margin-bottom: 2rem;
    transition: border-color .2s, color .2s;
}
.vs-back-btn:hover { border-color: var(--vs-blue); color: var(--vs-text); }

.vs-viz-inner {
    display: grid;
    grid-template-columns: 1fr 340px;
    gap: 1.75rem; align-items: start;
}

/* ─── VIZ MAIN (left pane) ───────────────────────────────────────────────────── */
.vs-viz-main {
    background: var(--vs-card);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius);
    padding: 2rem;
    display: flex; flex-direction: column; gap: 1.5rem;
}
.vs-viz-header { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; }
.vs-viz-title {
    font-size: 1.5rem; font-weight: 800;
    letter-spacing: -.03em;
}
.vs-color-legend { display: flex; align-items: center; gap: 1.25rem; flex-wrap: wrap; }

/* Bar chart */
.vs-bars-container {
    height: 300px;
    background: var(--vs-surface);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius-sm);
    display: flex; align-items: flex-end;
    padding: 1.25rem 1.25rem 0;
    gap: 2px; overflow: hidden;
}
.vs-bar {
    flex: 1; min-width: 2px;
    border-radius: 2px 2px 0 0;
    background: var(--vs-bar-default);
    transition: height .06s linear, background .08s;
}
.vs-bar.vs-state-compare {
    background: var(--vs-bar-compare);
    box-shadow: 0 0 7px rgba(245,200,66,.5);
}
.vs-bar.vs-state-swap {
    background: var(--vs-bar-swap);
    box-shadow: 0 0 7px rgba(240,84,84,.5);
}
.vs-bar.vs-state-sorted { background: var(--vs-bar-sorted); }

/* Stats row */
.vs-stats-row {
    display: grid; grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
}
.vs-stat-box {
    background: var(--vs-surface);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius-sm);
    padding: 1rem; text-align: center;
}
.vs-stat-box-num {
    display: block;
    font-size: 1.5rem; font-weight: 800;
    font-family: var(--vs-mono); color: var(--vs-text);
    line-height: 1; margin-bottom: .375rem;
}
.vs-stat-box-label {
    font-size: .67rem; font-weight: 600; text-transform: uppercase;
    letter-spacing: .1em; color: var(--vs-text-3);
}

/* Controls */
.vs-controls { display: flex; gap: 1.5rem; flex-wrap: wrap; align-items: flex-start; }
.vs-ctrl-btns { display: flex; gap: .75rem; align-items: center; }

.vs-ctrl-btn {
    display: inline-flex; align-items: center; gap: .4rem;
    background: var(--vs-surface);
    border: 1px solid var(--vs-border);
    color: var(--vs-text-2);
    font-size: .85rem; font-weight: 500;
    padding: .625rem 1.25rem; border-radius: 7px;
    cursor: pointer;
    transition: border-color .2s, color .2s, transform .15s;
}
.vs-ctrl-btn:hover { border-color: var(--vs-border-light); color: var(--vs-text); transform: translateY(-1px); }
.vs-ctrl-btn:active { transform: translateY(0); }

.vs-ctrl-btn-primary {
    background: var(--vs-gradient); border-color: transparent;
    color: #fff; box-shadow: 0 2px 16px rgba(91,138,247,.25);
}
.vs-ctrl-btn-primary:hover { opacity: .88; box-shadow: 0 4px 24px rgba(91,138,247,.35); }

.vs-sliders { display: flex; flex-direction: column; gap: .875rem; flex: 1; min-width: 220px; }

.vs-slider-label {
    display: flex; align-items: center; gap: .75rem;
    font-size: .8rem; font-weight: 500; color: var(--vs-text-2);
}
.vs-slider-val {
    font-family: var(--vs-mono); font-size: .75rem;
    color: var(--vs-blue); min-width: 1.8rem; text-align: center;
}
.vs-slider {
    flex: 1; -webkit-appearance: none; appearance: none;
    height: 3px; background: var(--vs-border-light);
    border-radius: 2px; outline: none; cursor: pointer;
}
.vs-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 14px; height: 14px;
    background: var(--vs-blue); border-radius: 50%;
    cursor: pointer;
    box-shadow: 0 0 6px rgba(91,138,247,.55);
    transition: transform .15s;
}
.vs-slider::-webkit-slider-thumb:hover { transform: scale(1.25); }
.vs-slider::-moz-range-thumb {
    width: 14px; height: 14px;
    background: var(--vs-blue); border-radius: 50%;
    cursor: pointer; border: none;
    box-shadow: 0 0 6px rgba(91,138,247,.55);
}

/* ─── INFO PANEL (right pane) ────────────────────────────────────────────────── */
.vs-info-panel {
    display: flex; flex-direction: column; gap: 1.1rem;
    position: sticky; top: 80px;
}
.vs-complexity-grid {
    display: grid; grid-template-columns: 1fr 1fr;
    gap: .75rem;
}
.vs-complexity-card {
    background: var(--vs-card);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius-sm);
    padding: .875rem;
    display: flex; flex-direction: column; gap: .3rem;
}
.vs-complexity-label {
    font-size: .65rem; font-weight: 600;
    text-transform: uppercase; letter-spacing: .1em;
    color: var(--vs-text-3);
}
.vs-complexity-val {
    font-size: .925rem; font-weight: 700;
    font-family: var(--vs-mono); color: var(--vs-blue);
    line-height: 1.2;
}
.vs-complexity-val-worst { color: #f07070 !important; }

.vs-info-card {
    background: var(--vs-card);
    border: 1px solid var(--vs-border);
    border-radius: var(--vs-radius-sm);
    padding: 1.25rem;
}
.vs-info-card-title {
    font-size: .67rem; font-weight: 600;
    text-transform: uppercase; letter-spacing: .12em;
    color: var(--vs-text-3); margin-bottom: .75rem;
}
.vs-info-text {
    font-size: .875rem; line-height: 1.75;
    color: var(--vs-text-2);
}

/* Pseudocode */
.vs-pseudocode {
    font-family: var(--vs-mono);
    font-size: .76rem; line-height: 1.75;
    color: #c0c0e0; white-space: pre;
    overflow-x: auto; margin: 0;
    scrollbar-width: thin;
    scrollbar-color: var(--vs-border) transparent;
}
.vs-pseudocode .vs-line-active {
    display: block;
    background: rgba(91,138,247,.14);
    border-left: 2px solid var(--vs-blue);
    padding-left: .5rem; margin-left: -.5rem;
}

/* ─── FOOTER ─────────────────────────────────────────────────────────────────── */
.vs-footer {
    border-top: 1px solid var(--vs-border);
    padding: 1.75rem 0;
}
.vs-footer-inner {
    display: flex; align-items: center;
    justify-content: space-between; flex-wrap: wrap; gap: 1rem;
}
.vs-footer-logo { font-size: .9rem; font-weight: 700; }
.vs-footer-tagline { font-size: .8rem; color: var(--vs-text-3); }

/* ─── RESPONSIVE ─────────────────────────────────────────────────────────────── */
@media (max-width: 1080px) {
    .vs-viz-inner { grid-template-columns: 1fr; }
    .vs-info-panel { position: static; }
    .vs-complexity-grid { grid-template-columns: repeat(4, 1fr); }
}

@media (max-width: 900px) {
    .vs-algo-grid { grid-template-columns: repeat(2, 1fr); }
    .vs-hero-inner { grid-template-columns: 1fr; padding: 4rem 0; }
    .vs-hero-visual { display: none; }
}

@media (max-width: 640px) {
    .vs-container { padding: 0 1.25rem; }
    .vs-algo-grid { grid-template-columns: 1fr; }
    .vs-complexity-grid { grid-template-columns: 1fr 1fr; }
    .vs-controls { flex-direction: column; }
    .vs-ctrl-btns { flex-wrap: wrap; }
    .vs-nav-links { gap: 1rem; }
    .vs-nav-cta { display: none; }
}