/* ==========================================================
   DSA Visualizer — main stylesheet
   Light, modern, educational dashboard
   ========================================================== */

/* --- Design tokens --- */
:root {
    --bg:           #f6f8fc;
    --surface:      #ffffff;
    --surface-2:    #f0f3fa;
    --border:       #e3e8f0;

    --text:         #1f2937;
    --text-muted:   #5b6675;
    --text-light:   #8a94a6;

    --primary:      #4f6df5;
    --primary-soft: #e8edff;
    --primary-dark: #3b53d6;

    --accent:       #7c5cff;

    /* Operation color codes (as required by spec) */
    --compare:      #3b82f6;   /* blue   — comparisons */
    --swap:         #ef4444;   /* red    — swaps */
    --pointer:      #22c55e;   /* green  — current pointer */
    --sorted:       #a78bfa;   /* purple — finalized */

    --shadow-sm:    0 1px 2px rgba(20, 30, 60, 0.06);
    --shadow-md:    0 4px 14px rgba(20, 30, 60, 0.08);
    --shadow-lg:    0 10px 30px rgba(20, 30, 60, 0.10);

    --radius-sm:    8px;
    --radius:       12px;
    --radius-lg:    16px;

    --sidebar-w:    250px;
    --transition:   .25s ease;
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    background: var(--bg);
    color: var(--text);
    font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
    font-size: 15px;
    line-height: 1.5;
}

h1, h2, h3, h4 { margin: 0 0 .4em; font-weight: 600; }
p { margin: 0 0 .8em; }

/* ========== App layout ========== */
.app {
    display: flex;
    min-height: 100vh;
}

/* ========== Sidebar ========== */
.sidebar {
    width: var(--sidebar-w);
    background: var(--surface);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    position: sticky;
    top: 0;
    height: 100vh;
    transition: transform var(--transition);
    z-index: 20;
}

.brand {
    display: flex;
    gap: 12px;
    align-items: center;
    padding: 22px 20px;
    border-bottom: 1px solid var(--border);
}
.brand-logo {
    width: 40px; height: 40px;
    border-radius: 10px;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    color: #fff;
    display: flex; align-items: center; justify-content: center;
    font-weight: 700;
    box-shadow: var(--shadow-sm);
}
.brand-title { font-weight: 700; font-size: 15px; }
.brand-sub   { font-size: 12px; color: var(--text-muted); }

.nav {
    flex: 1;
    padding: 12px 10px;
    overflow-y: auto;
}
.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    margin: 2px 0;
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    text-decoration: none;
    font-size: 14px;
    transition: var(--transition);
}
.nav-item:hover {
    background: var(--surface-2);
    color: var(--text);
}
.nav-item.active {
    background: var(--primary-soft);
    color: var(--primary-dark);
    font-weight: 600;
}
.nav-icon { font-size: 17px; width: 22px; text-align: center; }

.sidebar-footer {
    padding: 14px 20px;
    border-top: 1px solid var(--border);
    color: var(--text-light);
    font-size: 11px;
}

/* ========== Main area ========== */
.main {
    flex: 1;
    min-width: 0;          /* prevents flex overflow */
    display: flex;
    flex-direction: column;
}

.topbar {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 18px 28px;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 10;
}
.page-title { font-size: 20px; margin: 0; }

.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 22px;
    cursor: pointer;
    color: var(--text);
}

.content {
    padding: 28px;
    max-width: 1300px;
    width: 100%;
    margin: 0 auto;
}

/* ========== Cards ========== */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 22px;
    margin-bottom: 22px;
    box-shadow: var(--shadow-sm);
}
.card h2 { font-size: 17px; margin-bottom: 14px; }
.card h3 { font-size: 15px; margin-bottom: 10px; color: var(--text-muted); }

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 18px;
}

/* ========== Controls ========== */
.controls {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    margin-bottom: 18px;
}
.controls label {
    font-size: 13px;
    color: var(--text-muted);
    margin-right: 4px;
}
.input, .select {
    padding: 9px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    font-size: 14px;
    color: var(--text);
    outline: none;
    transition: var(--transition);
}
.input:focus, .select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-soft);
}
.input { width: 90px; }
.input.wide { width: 240px; }

.btn {
    padding: 9px 16px;
    border: none;
    border-radius: var(--radius-sm);
    background: var(--primary);
    color: #fff;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}
.btn:hover { background: var(--primary-dark); }
.btn:disabled { background: var(--text-light); cursor: not-allowed; }

.btn.ghost {
    background: var(--surface-2);
    color: var(--text);
}
.btn.ghost:hover { background: var(--border); }

.btn.danger { background: var(--swap); }
.btn.danger:hover { background: #c93333; }

/* ========== Stats counters ========== */
.stats {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin: 14px 0;
}
.stat {
    flex: 1;
    min-width: 130px;
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    background: var(--surface-2);
    border: 1px solid var(--border);
}
.stat-label { font-size: 11px; text-transform: uppercase; letter-spacing: .5px; color: var(--text-muted); }
.stat-value { font-size: 22px; font-weight: 700; margin-top: 2px; }

.stat.blue   .stat-value { color: var(--compare); }
.stat.red    .stat-value { color: var(--swap); }
.stat.green  .stat-value { color: var(--pointer); }
.stat.purple .stat-value { color: var(--accent); }

/* ========== Visualization canvas areas ========== */
.viz {
    background: var(--surface-2);
    border: 1px dashed var(--border);
    border-radius: var(--radius);
    padding: 24px 24px 12px;
    min-height: 220px;
    display: flex;
    flex-direction: row;
    align-items: flex-end;
    justify-content: center;
    gap: 6px;
    overflow-x: auto;
    transition: var(--transition);
}

/* --- Array bars (sorting/searching) --- */
.bar-wrap {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    transition: transform var(--transition);
}
.bar {
    width: 36px;
    background: linear-gradient(180deg, #94a3b8, #64748b);
    border-radius: 6px 6px 0 0;
    transition: height var(--transition), background var(--transition), transform var(--transition);
    position: relative;
}
.bar-label {
    font-size: 12px;
    color: var(--text-muted);
    font-weight: 600;
}

.bar.compare { background: linear-gradient(180deg, #60a5fa, var(--compare)); transform: translateY(-4px); }
.bar.swap    { background: linear-gradient(180deg, #fca5a5, var(--swap));    transform: translateY(-4px); }
.bar.pointer { background: linear-gradient(180deg, #86efac, var(--pointer)); }
.bar.sorted  { background: linear-gradient(180deg, #c4b5fd, var(--sorted));  }
.bar.pivot   { background: linear-gradient(180deg, #fcd34d, #f59e0b); }
/* Binary search specific */
.bar.mid     { background: linear-gradient(180deg, #fdba74, #f97316); transform: translateY(-4px); } /* orange = mid element */
.bar.found   { background: linear-gradient(180deg, #86efac, var(--pointer)); transform: translateY(-6px); } /* green = found */
.bar.dropped { opacity: 0.28; filter: grayscale(60%); }  /* dimmed = eliminated half */

/* --- Stack / Queue blocks --- */
.block-row {
    display: flex;
    flex-direction: row;
    gap: 8px;
    align-items: center;
    min-height: 120px;
    justify-content: center;
    flex-wrap: wrap;
}
.block-row.vertical { flex-direction: column-reverse; }    /* Stack grows up */

.block {
    min-width: 60px;
    height: 60px;
    background: var(--surface);
    border: 2px solid var(--primary);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    color: var(--primary-dark);
    box-shadow: var(--shadow-sm);
    transition: transform var(--transition), background var(--transition), border-color var(--transition);
    position: relative;
}
.block.new     { animation: pop-in .35s ease; border-color: var(--pointer); background: #e8fff0; }
.block.removed { animation: pop-out .35s ease forwards; }
.block.top     { border-color: var(--pointer); }
.block.top::after {
    content: "TOP";
    position: absolute;
    top: -22px;
    left: 50%; transform: translateX(-50%);
    font-size: 10px; font-weight: 700;
    color: var(--pointer);
    letter-spacing: .5px;
}
.block.front::before, .block.rear::after {
    position: absolute;
    top: -22px;
    font-size: 10px; font-weight: 700;
    letter-spacing: .5px;
    color: var(--pointer);
}
.block.front::before { content: "FRONT"; left: 50%; transform: translateX(-50%); }
.block.rear::after   { content: "REAR";  left: 50%; transform: translateX(-50%); color: var(--accent); }

@keyframes pop-in {
    from { transform: scale(.6); opacity: 0; }
    to   { transform: scale(1);  opacity: 1; }
}
@keyframes pop-out {
    to { transform: scale(.4) translateY(-30px); opacity: 0; }
}

/* --- Linked list arrows --- */
.arrow {
    color: var(--text-muted);
    font-size: 24px;
    font-weight: bold;
}

/* --- Tree --- */
.tree-canvas {
    width: 100%;
    min-height: 320px;
    overflow: auto;
}

/* ========== Step log ========== */
.steplog {
    background: var(--surface-2);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    margin-top: 14px;
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 13px;
    color: var(--text);
    min-height: 44px;
}
.steplog .log-line { padding: 2px 0; }
.steplog .log-line.current { color: var(--primary); font-weight: 600; }

/* ========== Complexity / charts ========== */
.chart-wrap {
    position: relative;
    height: 380px;
    width: 100%;
}
.table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 12px;
    font-size: 14px;
}
.table th, .table td {
    text-align: left;
    padding: 10px 14px;
    border-bottom: 1px solid var(--border);
}
.table th {
    background: var(--surface-2);
    font-weight: 600;
    color: var(--text-muted);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: .4px;
}
.table tr:hover td { background: var(--surface-2); }

/* ========== Legend ========== */
.legend {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin: 10px 0 16px;
    font-size: 12px;
    color: var(--text-muted);
}
.legend-item { display: inline-flex; align-items: center; gap: 6px; }
.legend-dot {
    width: 12px; height: 12px; border-radius: 3px;
    display: inline-block;
}
.dot-compare { background: var(--compare); }
.dot-swap    { background: var(--swap); }
.dot-pointer { background: var(--pointer); }
.dot-sorted  { background: var(--sorted); }
.dot-pivot   { background: #f59e0b; }
.dot-mid     { background: #f97316; }
.dot-dropped { background: #94a3b8; opacity: 0.4; }

/* ========== Hero / Home ========== */
.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    color: #fff;
    padding: 36px;
    border-radius: var(--radius-lg);
    margin-bottom: 22px;
    box-shadow: var(--shadow-md);
}
.hero h2 { font-size: 26px; margin-bottom: 0; color: #fff; }
.hero p  { color: rgba(255,255,255,.92); max-width: 700px; }

.feature-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 22px 18px;
    text-decoration: none;
    color: var(--text);
    transition: var(--transition);
    display: block;
    text-align: center;
}
.feature-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary);
}
.feature-icon  { font-size: 32px; margin-bottom: 8px; }
.feature-title { font-weight: 600; font-size: 15px; }
.feature-desc  { font-size: 13px; color: var(--text-muted); margin-top: 4px; }

/* DS symbols row — decorative icons only, no links */
.ds-symbols {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
    padding: 28px 24px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    margin-top: 4px;
}
.ds-symbols span {
    font-size: 36px;
    opacity: 0.7;
    cursor: default;
    transition: opacity var(--transition), transform var(--transition);
    user-select: none;
}
.ds-symbols span:hover { opacity: 1; transform: scale(1.15); }

/* ========== Responsive ========== */
@media (max-width: 900px) {
    .sidebar {
        position: fixed;
        transform: translateX(-100%);
    }
    .sidebar.open { transform: translateX(0); }
    .menu-toggle  { display: block; }
    .content      { padding: 18px; }
}

/* ========== Utility ========== */
.row { display: flex; gap: 16px; flex-wrap: wrap; align-items: center; }
.muted { color: var(--text-muted); font-size: 13px; }
.tag {
    display: inline-block;
    background: var(--primary-soft);
    color: var(--primary-dark);
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 11px;
    font-weight: 600;
}