/* =============================================
   Kruskal's MST — Premium Stylesheet
   ============================================= */

:root {
    --bg-primary: #070b16;
    --bg-secondary: #0b1326;
    --bg-card: rgba(17, 24, 39, 0.7);
    --bg-card-solid: #111827;
    --bg-input: #0b1326;
    --bg-glass: rgba(255, 255, 255, 0.03);
    --border: rgba(255, 255, 255, 0.06);
    --border-hover: rgba(255, 255, 255, 0.12);
    --border-accent: rgba(56, 189, 248, 0.35);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --accent-blue: #38bdf8;
    --accent-purple: #94a3ff;
    --accent-green: #22c55e;
    --accent-orange: #f59e0b;
    --accent-red: #f87171;
    --accent-cyan: #22d3ee;
    --accent-copper: #f97316;
    --gradient-primary: linear-gradient(135deg, #38bdf8 0%, #94a3ff 45%, #22c55e 100%);
    --gradient-btn: linear-gradient(135deg, #0ea5e9, #1d4ed8);
    --gradient-btn-hover: linear-gradient(135deg, #0284c7, #1e40af);
    --gradient-green: linear-gradient(135deg, #22c55e, #16a34a);
    --gradient-hero: linear-gradient(160deg, #060a14 0%, #0b1326 40%, #0c172e 100%);
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.4);
    --shadow-md: 0 4px 20px rgba(0,0,0,0.5);
    --shadow-lg: 0 8px 40px rgba(0,0,0,0.6);
    --shadow-glow-blue: 0 0 30px rgba(96,165,250,0.12);
    --shadow-glow-purple: 0 0 30px rgba(167,139,250,0.12);
    --shadow-glow-green: 0 0 30px rgba(52,211,153,0.12);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --font-main: 'Trebuchet MS', 'Candara', 'Franklin Gothic Medium', 'Segoe UI', sans-serif;
    --font-display: 'Palatino Linotype', 'Book Antiqua', 'Garamond', serif;
    --font-mono: 'Consolas', 'Lucida Console', 'Courier New', monospace;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
    font-family: var(--font-main);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    inset: 0;
    background-image:
        linear-gradient(transparent 24px, rgba(56, 189, 248, 0.05) 25px),
        linear-gradient(90deg, transparent 24px, rgba(56, 189, 248, 0.05) 25px);
    background-size: 25px 25px;
    pointer-events: none;
    z-index: 0;
}

/* ============================
   TOP NAVIGATION
   ============================ */
.top-nav {
    position: sticky;
    top: 0;
    z-index: 5;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 12px 24px;
    background: rgba(7, 11, 22, 0.75);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
}

.nav-brand {
    font-family: var(--font-display);
    font-weight: 800;
    font-size: 1rem;
    letter-spacing: 0.02em;
    color: var(--text-primary);
}

.nav-links {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 6px 10px;
    border-radius: 999px;
    border: 1px solid transparent;
    transition: var(--transition);
}

.nav-links a:hover,
.nav-links a:focus-visible {
    color: var(--text-primary);
    border-color: rgba(56, 189, 248, 0.35);
    background: rgba(56, 189, 248, 0.1);
    outline: none;
}

/* ============================
   HERO SECTION
   ============================ */
#hero {
    position: relative;
    background: var(--gradient-hero);
    padding: 80px 24px 64px;
    text-align: center;
    overflow: hidden;
    border-bottom: 1px solid var(--border);
    z-index: 1;
}

.hero-bg-shapes {
    position: absolute;
    inset: 0;
    pointer-events: none;
    overflow: hidden;
}

.shape {
    position: absolute;
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.15;
    animation: float 12s ease-in-out infinite;
}

.shape-1 {
    width: 500px; height: 500px;
    background: #3b82f6;
    top: -120px; left: -80px;
    animation-delay: 0s;
}

.shape-2 {
    width: 400px; height: 400px;
    background: #8b5cf6;
    top: 50px; right: -100px;
    animation-delay: -4s;
}

.shape-3 {
    width: 350px; height: 350px;
    background: #10b981;
    bottom: -100px; left: 40%;
    animation-delay: -8s;
}

@keyframes float {
    0%, 100% { transform: translateY(0) scale(1); }
    50% { transform: translateY(-30px) scale(1.05); }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}

.hero-badge {
    display: inline-block;
    background: rgba(96,165,250,0.1);
    border: 1px solid rgba(96,165,250,0.2);
    color: var(--accent-blue);
    font-size: 0.72rem;
    font-weight: 600;
    padding: 6px 18px;
    border-radius: 30px;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 20px;
}

.hero-pills {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
    margin-bottom: 18px;
}

.hero-pill {
    font-size: 0.68rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-secondary);
    border: 1px solid rgba(56, 189, 248, 0.2);
    background: rgba(56, 189, 248, 0.08);
    padding: 6px 12px;
    border-radius: 999px;
}

#hero h1 {
    font-family: var(--font-display);
    font-size: clamp(2.2rem, 5vw, 3.5rem);
    font-weight: 900;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.03em;
    line-height: 1.15;
    margin-bottom: 12px;
}

.hero-subtitle {
    font-size: 1.05rem;
    color: var(--text-secondary);
    max-width: 520px;
    margin: 0 auto 36px;
    line-height: 1.6;
}

.hero-stats {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0;
    flex-wrap: wrap;
    background: var(--bg-glass);
    backdrop-filter: blur(16px);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    padding: 20px 32px;
    margin-bottom: 32px;
    box-shadow: 0 10px 30px rgba(10, 20, 40, 0.35);
}

.hero-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 0 28px;
}

.hero-stat-divider {
    width: 1px;
    height: 36px;
    background: var(--border);
}

.stat-value {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.stat-label {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-top: 2px;
}

.hero-cta {
    display: inline-block;
    padding: 14px 36px;
    background: var(--gradient-btn);
    color: #fff;
    text-decoration: none;
    border-radius: var(--radius-md);
    font-weight: 700;
    font-size: 0.95rem;
    transition: var(--transition);
    box-shadow: 0 4px 24px rgba(59,130,246,0.3);
    border: 1px solid rgba(56, 189, 248, 0.35);
}

.hero-cta:hover {
    background: var(--gradient-btn-hover);
    transform: translateY(-2px);
    box-shadow: 0 8px 32px rgba(59,130,246,0.4);
}

.hero-cta:focus-visible {
    outline: none;
    box-shadow: 0 0 0 3px rgba(56, 189, 248, 0.3), 0 8px 32px rgba(59,130,246,0.4);
}

/* ============================
   MAIN & SECTIONS
   ============================ */
#app-main {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 24px 80px;
    position: relative;
    z-index: 1;
}

.section {
    padding: 60px 0;
}

.section + .section {
    border-top: 1px solid var(--border);
}

.section-header {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 36px;
}

.section-number {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--accent-blue);
    background: rgba(96,165,250,0.08);
    border: 1px solid rgba(96,165,250,0.15);
    width: 36px;
    height: 36px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.section-header h2 {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 800;
    letter-spacing: -0.02em;
}

/* ============================
   EXPLANATION CARDS (Section 01)
   ============================ */
.explanation-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 20px;
}

.explanation-card {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 28px 24px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.explanation-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: var(--transition);
}

.explanation-card:hover {
    border-color: var(--border-hover);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.explanation-card:hover::before { opacity: 1; }

.card-icon {
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--accent-blue);
    background: rgba(56, 189, 248, 0.12);
    border: 1px solid rgba(56, 189, 248, 0.25);
    border-radius: 999px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 6px 12px;
    margin-bottom: 14px;
}

.explanation-card h3 {
    font-size: 1.05rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.explanation-card p {
    font-size: 0.88rem;
    color: var(--text-secondary);
    line-height: 1.65;
}

.explanation-card strong {
    color: var(--text-primary);
}

/* ============================
   TIMELINE (Section 02)
   ============================ */
.steps-timeline {
    position: relative;
    padding-left: 36px;
}

.steps-timeline::before {
    content: '';
    position: absolute;
    left: 17px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--accent-blue), var(--accent-purple), var(--accent-green), var(--accent-orange), var(--accent-red));
    border-radius: 2px;
}

.timeline-step {
    position: relative;
    padding: 0 0 32px 32px;
}

.timeline-step:last-child { padding-bottom: 0; }

.timeline-dot {
    position: absolute;
    left: -36px;
    top: 2px;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--bg-primary);
    border: 2px solid var(--dot-color, var(--accent-blue));
    color: var(--dot-color, var(--accent-blue));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.78rem;
    font-weight: 800;
    font-family: var(--font-mono);
    z-index: 1;
}

.timeline-content h4 {
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 4px;
}

.timeline-content p {
    font-size: 0.88rem;
    color: var(--text-secondary);
}

.timeline-content code {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    background: rgba(96,165,250,0.1);
    color: var(--accent-blue);
    padding: 2px 8px;
    border-radius: 5px;
}

/* ============================
   COMPLEXITY (Section 03)
   ============================ */
.complexity-layout {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 24px;
    align-items: start;
}

.complexity-chart-container {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 28px;
}

.complexity-chart-container h3 {
    font-size: 0.95rem;
    font-weight: 700;
    margin-bottom: 22px;
}

.bar-chart {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.bar-item {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.bar-label {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.bar-track {
    background: rgba(255,255,255,0.04);
    border-radius: 8px;
    height: 32px;
    overflow: hidden;
    position: relative;
}

.bar-fill {
    height: 100%;
    border-radius: 8px;
    background: var(--bar-color);
    display: flex;
    align-items: center;
    padding: 0 12px;
    font-family: var(--font-mono);
    font-size: 0.72rem;
    font-weight: 600;
    color: #fff;
    width: 0;
    transition: width 1.2s cubic-bezier(0.22, 1, 0.36, 1);
    white-space: nowrap;
}

.bar-fill.bar-total {
    background: linear-gradient(90deg, var(--bar-color), #f59e0b);
}

.chart-note {
    font-size: 0.72rem;
    color: var(--text-muted);
    margin-top: 16px;
    font-style: italic;
}

.complexity-cards {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.stat-card {
    display: flex;
    align-items: center;
    gap: 16px;
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 18px 20px;
    transition: var(--transition);
}

.stat-card:hover {
    border-color: var(--border-hover);
    transform: translateX(4px);
}

.stat-card-icon {
    font-size: 1.5rem;
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: rgba(96,165,250,0.08);
    border: 1px solid var(--card-accent, var(--accent-blue));
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    filter: drop-shadow(0 0 8px color-mix(in srgb, var(--card-accent) 30%, transparent));
}

.stat-card-title {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.stat-card-value {
    font-family: var(--font-mono);
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--text-primary);
}

.stat-card-desc {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 1px;
}

/* ============================
   COMPARISON TABLE (Section 04)
   ============================ */
.comparison-table-wrapper {
    overflow-x: auto;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
}

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

.comparison-table thead {
    background: rgba(255,255,255,0.03);
}

.comparison-table th {
    padding: 16px 20px;
    text-align: left;
    font-weight: 700;
    font-size: 0.82rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
}

.comparison-table td {
    padding: 14px 20px;
    border-bottom: 1px solid var(--border);
    color: var(--text-secondary);
}

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

.comparison-table tbody tr {
    transition: var(--transition);
}

.comparison-table tbody tr:hover {
    background: rgba(255,255,255,0.02);
}

.highlight-col {
    color: var(--accent-blue) !important;
    font-weight: 600 !important;
    background: rgba(96,165,250,0.04);
}

/* ============================
   APPLICATIONS (Section 05)
   ============================ */
.apps-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 18px;
}

.app-card {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 24px 20px;
    transition: var(--transition);
}

.app-card:hover {
    border-color: var(--border-hover);
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.app-icon {
    font-size: 1.6rem;
    margin-bottom: 12px;
}

.app-card h4 {
    font-size: 0.95rem;
    font-weight: 700;
    margin-bottom: 6px;
}

.app-card p {
    font-size: 0.82rem;
    color: var(--text-secondary);
    line-height: 1.55;
    margin-bottom: 14px;
}

.app-bar {
    position: relative;
    height: 6px;
    background: rgba(255,255,255,0.04);
    border-radius: 4px;
    overflow: hidden;
}

.app-bar::after {
    content: '';
    position: absolute;
    left: 0; top: 0; bottom: 0;
    width: var(--app-pct);
    background: var(--app-color);
    border-radius: 4px;
    transition: width 1s cubic-bezier(0.22, 1, 0.36, 1);
}

.app-bar span {
    position: absolute;
    right: 0;
    top: -20px;
    font-size: 0.65rem;
    color: var(--text-muted);
    font-weight: 600;
}

/* ============================
   TEST CASES (Section 05)
   ============================ */
.testcases-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 18px;
    margin-bottom: 24px;
}

.testcase-card {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 20px 18px;
    transition: var(--transition);
}

.testcase-card:hover {
    border-color: var(--border-hover);
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.testcase-title {
    font-size: 0.95rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.testcase-block {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-secondary);
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 10px 12px;
    line-height: 1.5;
    margin-bottom: 10px;
}

.testcase-steps {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.testcase-result {
    font-size: 0.82rem;
    color: var(--accent-green);
    font-weight: 600;
}

.rules-card {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 22px;
}

.rules-card h3 {
    font-size: 0.95rem;
    font-weight: 700;
    margin-bottom: 12px;
}

.rules-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.86rem;
}

.rules-table th,
.rules-table td {
    padding: 12px 14px;
    border-bottom: 1px solid var(--border);
    text-align: left;
}

.rules-table th {
    color: var(--text-secondary);
    text-transform: uppercase;
    font-size: 0.72rem;
    letter-spacing: 0.05em;
}

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

/* ============================
   REAL-WORLD APPLICATIONS (Section 06)
   ============================ */
.apps-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.app-item {
    display: flex;
    gap: 14px;
    align-items: flex-start;
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 16px 18px;
    transition: var(--transition);
}

.app-item:hover {
    border-color: var(--border-hover);
    transform: translateY(-2px);
}

.app-body h4 {
    font-size: 0.92rem;
    font-weight: 700;
    margin-bottom: 6px;
}

.app-body p {
    font-size: 0.82rem;
    color: var(--text-secondary);
    margin-bottom: 6px;
}

.app-meta {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.apps-summary {
    background: var(--bg-glass);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 22px;
}

.apps-summary h3 {
    font-size: 0.95rem;
    font-weight: 700;
    margin-bottom: 12px;
}

.apps-summary-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.86rem;
}

.apps-summary-table th,
.apps-summary-table td {
    padding: 12px 14px;
    border-bottom: 1px solid var(--border);
    text-align: left;
}

.apps-summary-table th {
    color: var(--text-secondary);
    text-transform: uppercase;
    font-size: 0.72rem;
    letter-spacing: 0.05em;
}

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

/* ============================
   PANELS (Visualizer Cards)
   ============================ */
.panel {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    margin-bottom: 20px;
    backdrop-filter: blur(12px);
}

.panel:hover {
    border-color: var(--border-hover);
}

.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 24px;
    border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,0.015);
    position: relative;
}

.panel-header::after {
    content: '';
    position: absolute;
    left: 24px;
    right: 24px;
    bottom: 0;
    height: 2px;
    background: linear-gradient(90deg, rgba(56,189,248,0.4), rgba(148,163,255,0.2), transparent);
}

.panel-header h3 {
    font-size: 1rem;
    font-weight: 700;
}

.panel-body { padding: 24px; }

/* ====== INPUT SECTION ====== */
.input-row {
    display: flex;
    gap: 16px;
    align-items: flex-end;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.input-group label {
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.input-group small {
    font-size: 0.65rem;
    color: var(--text-muted);
    display: block;
    margin-top: 2px;
}

.input-group input {
    width: 100px;
    padding: 10px 14px;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.88rem;
    transition: var(--transition);
    outline: none;
}

.input-group select {
    min-width: 260px;
    padding: 10px 12px;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--font-main);
    font-size: 0.85rem;
    outline: none;
    transition: var(--transition);
}

.input-group select:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(56, 189, 248, 0.18);
}

.preset-row {
    display: flex;
    gap: 12px;
    align-items: flex-end;
    flex-wrap: wrap;
    margin-bottom: 18px;
}

.preset-group label {
    display: block;
}

.tool-row {
    display: flex;
    gap: 12px;
    align-items: flex-end;
    flex-wrap: wrap;
    margin-bottom: 18px;
}

.toggle-group {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    align-items: center;
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.toggle input {
    margin-right: 6px;
    accent-color: var(--accent-blue);
}

.input-group input:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(96,165,250,0.12);
}

.input-group input:focus-visible,
.input-group select:focus-visible,
.btn:focus-visible {
    outline: none;
    box-shadow: 0 0 0 3px rgba(56, 189, 248, 0.3);
}

.edge-inputs-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 10px;
    margin-bottom: 20px;
    max-height: 280px;
    overflow-y: auto;
    padding-right: 4px;
}

.builder-panel {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    margin-bottom: 18px;
}

.builder-header {
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-bottom: 10px;
}

.builder-controls {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-bottom: 10px;
}

.builder-controls .btn {
    min-width: 92px;
}

.builder-controls .btn.active {
    border-color: rgba(56, 189, 248, 0.4);
    color: var(--text-primary);
    background: rgba(56, 189, 248, 0.12);
}

.builder-hint {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.validation-panel {
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.02);
    padding: 14px 16px;
    margin-bottom: 18px;
}

.validation-title {
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-bottom: 10px;
}

.validation-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.validation-list li.ok {
    color: var(--accent-green);
}

.validation-list li.warn {
    color: var(--accent-orange);
}

.validation-list li.err {
    color: var(--accent-red);
}

.export-panel {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 14px;
}

.import-panel {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 14px;
    margin-bottom: 10px;
}

.import-panel textarea {
    width: 100%;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.8rem;
    padding: 10px 12px;
    margin-bottom: 10px;
}

.import-actions {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.edge-inputs-container::-webkit-scrollbar { width: 4px; }
.edge-inputs-container::-webkit-scrollbar-track { background: var(--bg-primary); border-radius: 4px; }
.edge-inputs-container::-webkit-scrollbar-thumb { background: var(--border-hover); border-radius: 4px; }

.edge-input-row {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--bg-input);
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    transition: var(--transition);
}

.edge-input-row:focus-within {
    border-color: var(--border-accent);
    box-shadow: 0 0 0 2px rgba(56, 189, 248, 0.12);
}

.edge-input-row:hover { border-color: var(--border-hover); }

.edge-input-row .edge-label {
    font-size: 0.68rem;
    font-weight: 700;
    color: var(--text-muted);
    font-family: var(--font-mono);
    min-width: 24px;
    text-align: center;
}

.edge-input-row input {
    width: 52px;
    padding: 6px 8px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.82rem;
    text-align: center;
    outline: none;
    transition: var(--transition);
}

.edge-input-row input:focus {
    border-color: var(--accent-purple);
    box-shadow: 0 0 0 2px rgba(167,139,250,0.12);
}

.edge-input-row .separator {
    color: var(--text-muted);
    font-size: 0.72rem;
}

/* ====== BUTTONS ====== */
.btn {
    padding: 10px 22px;
    border: none;
    border-radius: var(--radius-sm);
    font-family: var(--font-main);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
    position: relative;
}

.btn-primary {
    background: var(--gradient-btn);
    color: #fff;
    box-shadow: 0 4px 20px rgba(59,130,246,0.25);
}

.btn-primary:hover {
    background: var(--gradient-btn-hover);
    transform: translateY(-1px);
    box-shadow: 0 6px 28px rgba(59,130,246,0.35);
}

.btn-secondary {
    background: rgba(96,165,250,0.1);
    color: var(--accent-blue);
    border: 1px solid rgba(96,165,250,0.2);
}

.btn-secondary:hover { background: rgba(96,165,250,0.18); }

.btn-outline {
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
}

.btn-outline:hover {
    background: rgba(255,255,255,0.04);
    border-color: var(--border-hover);
    color: var(--text-primary);
}

.action-row { display: flex; gap: 12px; justify-content: flex-end; flex-wrap: wrap; }

/* ====== SORTED EDGE CHIPS ====== */
.sorted-edges-section { margin-bottom: 20px; }
.sorted-edges-section h4 {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 10px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.edge-chips { display: flex; flex-wrap: wrap; gap: 8px; }

.edge-chip {
    display: inline-flex;
    align-items: center;
    padding: 6px 14px;
    border-radius: 20px;
    font-family: var(--font-mono);
    font-size: 0.76rem;
    font-weight: 500;
    border: 1px solid var(--border);
    background: var(--bg-input);
    color: var(--text-secondary);
    transition: var(--transition);
}

.edge-chip.processing {
    border-color: var(--accent-orange);
    color: var(--accent-orange);
    background: rgba(251,191,36,0.06);
    animation: chipPulse 0.5s ease;
}

.edge-chip.accepted {
    border-color: var(--accent-green);
    color: var(--accent-green);
    background: rgba(52,211,153,0.06);
}

.edge-chip.rejected {
    border-color: var(--accent-red);
    color: var(--accent-red);
    background: rgba(248,113,113,0.06);
    text-decoration: line-through;
    opacity: 0.55;
}

@keyframes chipPulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.06); }
    100% { transform: scale(1); }
}

/* ====== STEPS LOG ====== */
.steps-log { display: flex; flex-direction: column; gap: 8px; margin-bottom: 20px; }

.playback-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    padding: 12px;
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border);
    margin-bottom: 16px;
}

.guide-row {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    align-items: center;
    margin-bottom: 12px;
}

.guide-box {
    flex: 1 1 260px;
    font-size: 0.78rem;
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 10px 12px;
    background: rgba(255, 255, 255, 0.02);
}

.compare-box {
    margin-bottom: 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 12px 14px;
    font-size: 0.82rem;
    color: var(--text-secondary);
    background: rgba(255, 255, 255, 0.02);
}

.playback-controls .btn {
    min-width: 110px;
    justify-content: center;
}

.speed-control {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.speed-control input[type="range"] {
    accent-color: var(--accent-blue);
}

.key-hint {
    font-size: 0.72rem;
    color: var(--text-muted);
    margin-left: auto;
}

.step-entry {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    animation: slideIn 0.35s ease;
}

.step-entry .step-icon {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 0.72rem;
    font-weight: 700;
    border: 1px solid currentColor;
}

.step-entry.accepted {
    background: rgba(52,211,153,0.06);
    border-left: 3px solid var(--accent-green);
    color: var(--accent-green);
}

.step-entry.rejected {
    background: rgba(248,113,113,0.04);
    border-left: 3px solid var(--accent-red);
    color: var(--accent-red);
    opacity: 0.65;
}

.step-entry .step-icon { font-size: 1rem; flex-shrink: 0; }
.step-entry .step-text { font-family: var(--font-mono); font-size: 0.8rem; }

@keyframes slideIn {
    from { opacity: 0; transform: translateX(-12px); }
    to { opacity: 1; transform: translateX(0); }
}

/* ====== RESULT BOX ====== */
.result-box {
    background: linear-gradient(135deg, rgba(52,211,153,0.08), rgba(96,165,250,0.08));
    border: 1px solid rgba(52,211,153,0.2);
    border-radius: var(--radius-md);
    padding: 24px 28px;
    text-align: center;
    animation: fadeInUp 0.5s ease;
    margin-bottom: 20px;
}

.result-label {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 6px;
}

.result-cost {
    font-size: 2.5rem;
    font-weight: 900;
    background: var(--gradient-green);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.result-note {
    font-size: 0.78rem;
    color: var(--text-muted);
    margin-top: 6px;
}

@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ====== LIVE STATS ====== */
.live-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 14px;
}

.live-stat {
    background: rgba(255,255,255,0.02);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 16px;
    text-align: center;
    transition: var(--transition);
}

.live-stat-num {
    display: block;
    font-family: var(--font-mono);
    font-size: 1.6rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.live-stat-label {
    display: block;
    font-size: 0.68rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: 4px;
}

/* ====== CANVAS ====== */
.canvas-body {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
    width: 100%;
}

.canvas-legend {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
    padding: 8px 12px;
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border);
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.76rem;
    color: var(--text-secondary);
}

.legend-dot { width: 10px; height: 10px; border-radius: 50%; }
.dot-default { background: #475569; }
.dot-mst { background: var(--accent-green); }
.dot-rejected { background: var(--accent-red); }

#graph-canvas {
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    max-width: 100%;
    height: auto;
    box-shadow: inset 0 0 0 1px rgba(56, 189, 248, 0.08);
}

/* ====== PRESENTATION MODE ====== */
body.presentation .top-nav,
body.presentation #app-footer {
    display: none;
}

body.presentation #app-main {
    max-width: 1200px;
}

body.presentation #hero {
    padding-top: 40px;
}

/* ====== FOOTER ====== */
#app-footer {
    text-align: center;
    padding: 28px 24px;
    color: var(--text-muted);
    font-size: 0.72rem;
    border-top: 1px solid var(--border);
    position: relative;
    z-index: 1;
}

/* ====== UTILITY ====== */
.hidden { display: none !important; }

.error-message {
    background: rgba(248,113,113,0.08);
    border: 1px solid rgba(248,113,113,0.3);
    border-left: 3px solid var(--accent-red);
    border-radius: var(--radius-sm);
    padding: 14px 16px;
    color: var(--accent-red);
    font-size: 0.85rem;
    line-height: 1.5;
    animation: slideIn 0.35s ease;
}

.error-message strong {
    font-weight: 700;
    display: block;
    margin-bottom: 6px;
}

/* ====== SCROLL ANIMATIONS ====== */
.animate-in {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.animate-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ====== RESPONSIVE ====== */
@media (max-width: 768px) {
    .top-nav {
        flex-direction: column;
        align-items: flex-start;
    }

    .nav-links {
        gap: 6px;
    }
    #hero { padding: 50px 20px 40px; }
    #hero h1 { font-size: 2rem; }

    .hero-stats {
        flex-direction: column;
        gap: 14px;
        padding: 20px;
    }

    .hero-stat-divider { width: 60px; height: 1px; }

    .complexity-layout {
        grid-template-columns: 1fr;
    }

    .live-stats {
        grid-template-columns: repeat(2, 1fr);
    }

    .section-header h2 { font-size: 1.2rem; }

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

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

    .input-group select {
        width: 100%;
    }

    .playback-controls {
        flex-direction: column;
        align-items: stretch;
    }

    .export-panel {
        flex-direction: column;
    }

    .key-hint {
        margin-left: 0;
        text-align: left;
    }
}

@media (max-width: 500px) {
    .input-row { flex-direction: column; align-items: stretch; }
    .input-group input { width: 100%; }
    .edge-inputs-container { grid-template-columns: 1fr; }
    .action-row { flex-direction: column; }
    .action-row .btn { width: 100%; justify-content: center; }
    .live-stats { grid-template-columns: 1fr 1fr; }
    .apps-grid { grid-template-columns: 1fr; }
    .playback-controls .btn { width: 100%; justify-content: center; }
}