/* ============================================
   RankBridge — Design System
   ============================================ */

:root {
    --bg-primary: #0a0e1a;
    --bg-secondary: #111827;
    --bg-card: rgba(17, 24, 39, 0.7);
    --bg-card-hover: rgba(23, 32, 52, 0.8);
    --bg-input: rgba(15, 20, 35, 0.9);

    --text-primary: #f0f4ff;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --text-accent: #a5b4fc;

    --accent-1: #6366f1;
    --accent-2: #818cf8;
    --accent-3: #a5b4fc;
    --accent-glow: rgba(99, 102, 241, 0.3);
    --accent-gradient: linear-gradient(135deg, #6366f1, #8b5cf6, #a78bfa);

    --success: #34d399;
    --warning: #fbbf24;
    --error: #f87171;

    --border: rgba(148, 163, 184, 0.1);
    --border-accent: rgba(99, 102, 241, 0.3);

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 20px rgba(0,0,0,0.4);
    --shadow-lg: 0 8px 40px rgba(0,0,0,0.5);
    --shadow-glow: 0 0 40px var(--accent-glow);

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

    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; font-size: 16px; }

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

/* Ambient Background */
.ambient-bg {
    position: fixed; inset: 0; z-index: 0; pointer-events: none; overflow: hidden;
}
.ambient-orb {
    position: absolute; border-radius: 50%; filter: blur(120px); opacity: 0.15;
}
.orb-1 {
    width: 600px; height: 600px; top: -200px; left: -100px;
    background: radial-gradient(circle, #6366f1, transparent 70%);
    animation: orbFloat1 20s ease-in-out infinite;
}
.orb-2 {
    width: 500px; height: 500px; top: 40%; right: -150px;
    background: radial-gradient(circle, #8b5cf6, transparent 70%);
    animation: orbFloat2 25s ease-in-out infinite;
}
.orb-3 {
    width: 400px; height: 400px; bottom: -100px; left: 30%;
    background: radial-gradient(circle, #a78bfa, transparent 70%);
    animation: orbFloat3 22s ease-in-out infinite;
}
@keyframes orbFloat1 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(60px,80px)} }
@keyframes orbFloat2 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(-80px,-60px)} }
@keyframes orbFloat3 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(40px,-50px)} }

/* Header */
.header {
    position: fixed; top: 0; left: 0; right: 0; z-index: 100;
    background: rgba(10, 14, 26, 0.8);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    transition: var(--transition-base);
}
.header-inner {
    max-width: 1100px; margin: 0 auto; padding: 0 24px;
    display: flex; align-items: center; justify-content: space-between; height: 64px;
}
.logo { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text-primary); }
.logo-icon { width: 28px; height: 28px; color: var(--accent-2); }
.logo-text { font-size: 1.15rem; font-weight: 700; letter-spacing: -0.02em; }
.nav { display: flex; gap: 8px; }
.nav-link {
    padding: 6px 16px; border-radius: var(--radius-full); font-size: 0.875rem; font-weight: 500;
    color: var(--text-secondary); text-decoration: none; transition: var(--transition-fast);
}
.nav-link:hover { color: var(--text-primary); background: rgba(255,255,255,0.05); }
.nav-link.active { color: var(--accent-3); background: rgba(99,102,241,0.1); }

/* Hero */
.hero {
    position: relative; z-index: 1; padding: 140px 24px 60px; text-align: center;
}
.hero-content { max-width: 720px; margin: 0 auto; }
.hero-badge {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 6px 16px; border-radius: var(--radius-full);
    background: rgba(99,102,241,0.1); border: 1px solid var(--border-accent);
    font-size: 0.8rem; font-weight: 500; color: var(--accent-3);
    margin-bottom: 24px;
    animation: fadeInUp 0.6s ease-out;
}
.badge-dot {
    width: 6px; height: 6px; border-radius: 50%; background: var(--success);
    animation: pulse 2s ease-in-out infinite;
}
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:0.4} }

.hero-title {
    font-size: clamp(2rem, 5vw, 3.2rem); font-weight: 800; line-height: 1.15;
    letter-spacing: -0.03em; margin-bottom: 16px;
    animation: fadeInUp 0.6s ease-out 0.1s both;
}
.hero-swap { color: var(--accent-2); }
.hero-highlight {
    background: var(--accent-gradient); -webkit-background-clip: text;
    -webkit-text-fill-color: transparent; background-clip: text;
}
.hero-subtitle {
    font-size: 1.05rem; color: var(--text-secondary); max-width: 560px; margin: 0 auto;
    line-height: 1.7; animation: fadeInUp 0.6s ease-out 0.2s both;
}
@keyframes fadeInUp { from{opacity:0;transform:translateY(16px)} to{opacity:1;transform:translateY(0)} }

/* Converter */
.converter-section { position: relative; z-index: 1; padding: 20px 24px 80px; }
.converter-container { max-width: 640px; margin: 0 auto; }

/* Mode Toggle */
.mode-toggle {
    position: relative; display: flex; padding: 4px; border-radius: var(--radius-full);
    background: var(--bg-secondary); border: 1px solid var(--border);
    margin-bottom: 32px; width: fit-content; margin-left: auto; margin-right: auto;
}
.mode-btn {
    position: relative; z-index: 2; padding: 10px 28px; border: none; background: none;
    font-family: var(--font-sans); font-size: 0.9rem; font-weight: 600;
    color: var(--text-secondary); cursor: pointer; border-radius: var(--radius-full);
    transition: var(--transition-base);
}
.mode-btn.active { color: var(--text-primary); }
.mode-btn:hover:not(.active) { color: var(--text-primary); }
.mode-slider {
    position: absolute; top: 4px; left: 4px; height: calc(100% - 8px);
    width: calc(50% - 4px); border-radius: var(--radius-full);
    background: var(--accent-1); transition: var(--transition-base);
    box-shadow: 0 0 20px var(--accent-glow);
}
.mode-slider.right { left: calc(50%); }

/* Converter Card */
.converter-card {
    position: relative; padding: 40px 36px; border-radius: var(--radius-xl);
    background: var(--bg-card);
    border: 1px solid var(--border);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    box-shadow: var(--shadow-lg);
    transition: var(--transition-slow);
    animation: fadeInUp 0.6s ease-out 0.3s both;
}
.converter-card:hover { border-color: var(--border-accent); }
.card-glow {
    position: absolute; top: -1px; left: 50%; transform: translateX(-50%);
    width: 200px; height: 2px; border-radius: 2px;
    background: var(--accent-gradient); opacity: 0.6;
}

/* Input */
.input-section { margin-bottom: 28px; }
.input-label {
    display: flex; align-items: center; gap: 8px; margin-bottom: 12px;
    font-size: 0.9rem; font-weight: 500; color: var(--text-secondary);
}
.label-icon { width: 16px; height: 16px; color: var(--accent-2); }
.input-wrapper {
    display: flex; gap: 12px; align-items: center;
}
.rank-input {
    flex: 1; padding: 16px 20px; border-radius: var(--radius-md);
    background: var(--bg-input); border: 1.5px solid var(--border);
    color: var(--text-primary); font-family: var(--font-mono); font-size: 1.25rem;
    font-weight: 500; letter-spacing: 0.02em;
    transition: var(--transition-fast); outline: none;
    -moz-appearance: textfield;
}
.rank-input::-webkit-outer-spin-button,
.rank-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.rank-input::placeholder { color: var(--text-muted); font-weight: 400; }
.rank-input:focus { border-color: var(--accent-1); box-shadow: 0 0 0 3px var(--accent-glow); }

.convert-btn {
    width: 54px; height: 54px; border-radius: var(--radius-md); border: none;
    background: var(--accent-gradient); cursor: pointer;
    display: flex; align-items: center; justify-content: center;
    transition: var(--transition-fast); flex-shrink: 0;
    box-shadow: 0 4px 15px var(--accent-glow);
}
.convert-btn:hover { transform: scale(1.05); box-shadow: 0 6px 25px var(--accent-glow); }
.convert-btn:active { transform: scale(0.97); }
.btn-arrow { width: 22px; height: 22px; color: white; }

.input-range-hint {
    margin-top: 8px; font-size: 0.78rem; color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Divider */
.card-divider { display: flex; align-items: center; gap: 16px; margin-bottom: 28px; }
.divider-line { flex: 1; height: 1px; background: var(--border); }
.divider-icon { color: var(--accent-2); opacity: 0.5; }
.divider-icon svg { width: 18px; height: 18px; }

/* Result */
.result-section { min-height: 140px; display: flex; align-items: center; justify-content: center; }
.result-placeholder {
    text-align: center; color: var(--text-muted); font-size: 0.9rem;
    display: flex; flex-direction: column; align-items: center; gap: 12px;
}
.placeholder-icon { width: 40px; height: 40px; opacity: 0.3; }

.result-display { text-align: center; width: 100%; }
.result-display.hidden { display: none; }
.result-label { font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 8px; font-weight: 500; }
.result-value {
    font-family: var(--font-mono); font-size: 2.8rem; font-weight: 700;
    background: var(--accent-gradient); -webkit-background-clip: text;
    -webkit-text-fill-color: transparent; background-clip: text;
    letter-spacing: -0.02em; line-height: 1.2;
    animation: resultPop 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}
@keyframes resultPop { from{transform:scale(0.8);opacity:0} to{transform:scale(1);opacity:1} }

.result-range {
    font-size: 0.85rem; color: var(--text-muted); margin-top: 6px;
    font-family: var(--font-mono);
}
.result-meta {
    display: flex; justify-content: center; gap: 32px; margin-top: 20px;
    padding-top: 20px; border-top: 1px solid var(--border);
}
.meta-item { text-align: center; }
.meta-label { display: block; font-size: 0.72rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 4px; }
.meta-value { font-size: 0.95rem; font-weight: 600; color: var(--text-primary); font-family: var(--font-mono); }

/* Warning */
.warning-banner {
    display: flex; align-items: flex-start; gap: 10px; margin-top: 20px;
    padding: 12px 16px; border-radius: var(--radius-md);
    background: rgba(251, 191, 36, 0.08); border: 1px solid rgba(251, 191, 36, 0.2);
    font-size: 0.82rem; color: var(--warning); line-height: 1.5;
}
.warning-banner.hidden { display: none; }
.warning-icon { width: 18px; height: 18px; flex-shrink: 0; margin-top: 1px; }

/* Quick Reference */
.quick-ref {
    margin-top: 48px; animation: fadeInUp 0.6s ease-out 0.5s both;
}
.quick-ref-title {
    font-size: 1rem; font-weight: 600; color: var(--text-secondary); margin-bottom: 16px; text-align: center;
}
.quick-ref-table-wrapper {
    overflow-x: auto; border-radius: var(--radius-lg);
    border: 1px solid var(--border); background: var(--bg-card);
}
.quick-ref-table {
    width: 100%; border-collapse: collapse; font-size: 0.85rem;
}
.quick-ref-table th {
    padding: 12px 16px; text-align: left; font-weight: 600;
    color: var(--text-secondary); font-size: 0.75rem; text-transform: uppercase;
    letter-spacing: 0.06em; border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,0.02);
}
.quick-ref-table td {
    padding: 10px 16px; border-bottom: 1px solid var(--border);
    font-family: var(--font-mono); font-size: 0.82rem; color: var(--text-primary);
}
.quick-ref-table tr:last-child td { border-bottom: none; }
.quick-ref-table tr:hover td { background: rgba(255,255,255,0.02); }

.branch-tag {
    display: inline-block; padding: 2px 10px; border-radius: var(--radius-full);
    font-size: 0.75rem; font-weight: 600; font-family: var(--font-sans);
}
.branch-tag.csai { background: rgba(99,102,241,0.15); color: #a5b4fc; }
.branch-tag.cse { background: rgba(52,211,153,0.15); color: #6ee7b7; }
.branch-tag.csam { background: rgba(251,191,36,0.15); color: #fcd34d; }
.branch-tag.csd { background: rgba(248,113,113,0.12); color: #fca5a5; }
.branch-tag.csb { background: rgba(167,139,250,0.15); color: #c4b5fd; }
.branch-tag.csss { background: rgba(45,212,191,0.15); color: #5eead4; }
.branch-tag.ece { background: rgba(251,146,60,0.15); color: #fdba74; }
.branch-tag.eve { background: rgba(148,163,184,0.15); color: #cbd5e1; }

/* Info Sections */
.info-section { position: relative; z-index: 1; padding: 80px 24px; }
.info-container { max-width: 960px; margin: 0 auto; }
.section-title {
    font-size: 2rem; font-weight: 800; text-align: center;
    letter-spacing: -0.03em; margin-bottom: 8px;
}
.section-subtitle {
    text-align: center; color: var(--text-secondary); font-size: 1rem; margin-bottom: 48px;
}

/* Steps */
.steps-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.step-card {
    padding: 28px; border-radius: var(--radius-lg); background: var(--bg-card);
    border: 1px solid var(--border); transition: var(--transition-base);
}
.step-card:hover { border-color: var(--border-accent); transform: translateY(-2px); }
.step-number {
    font-family: var(--font-mono); font-size: 0.8rem; font-weight: 600;
    color: var(--accent-2); margin-bottom: 12px;
}
.step-title { font-size: 1.05rem; font-weight: 700; margin-bottom: 8px; }
.step-desc { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.65; }

/* Stats */
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-bottom: 48px; }
.stat-card {
    text-align: center; padding: 24px 16px; border-radius: var(--radius-lg);
    background: var(--bg-card); border: 1px solid var(--border);
}
.stat-value {
    font-family: var(--font-mono); font-size: 1.6rem; font-weight: 700;
    color: var(--accent-3); margin-bottom: 4px;
}
.stat-label { font-size: 0.78rem; color: var(--text-secondary); }

/* Accuracy Table */
.accuracy-table-wrapper { margin-bottom: 40px; }
.accuracy-title { font-size: 1.1rem; font-weight: 700; margin-bottom: 16px; }
.accuracy-table {
    width: 100%; border-collapse: collapse; font-size: 0.85rem;
    border: 1px solid var(--border); border-radius: var(--radius-lg); overflow: hidden;
}
.accuracy-table th {
    padding: 12px 16px; text-align: left; font-weight: 600;
    color: var(--text-secondary); font-size: 0.75rem; text-transform: uppercase;
    letter-spacing: 0.05em; background: rgba(255,255,255,0.02);
    border-bottom: 1px solid var(--border);
}
.accuracy-table td {
    padding: 10px 16px; border-bottom: 1px solid var(--border); color: var(--text-primary);
}
.accuracy-table tr:last-child td { border-bottom: none; }
.zone-badge {
    display: inline-block; padding: 2px 10px; border-radius: var(--radius-full);
    font-size: 0.78rem; font-weight: 600; font-family: var(--font-mono);
}
.zone-badge.high { background: rgba(52,211,153,0.12); color: var(--success); }
.zone-badge.medium { background: rgba(251,191,36,0.12); color: var(--warning); }
.zone-badge.low { background: rgba(248,113,113,0.1); color: var(--error); }

/* Disclaimer */
.disclaimer {
    display: flex; align-items: flex-start; gap: 12px; padding: 16px 20px;
    border-radius: var(--radius-md); background: rgba(99,102,241,0.06);
    border: 1px solid var(--border-accent); font-size: 0.85rem;
    color: var(--text-secondary); line-height: 1.6;
}
.disclaimer-icon { width: 20px; height: 20px; flex-shrink: 0; color: var(--accent-2); margin-top: 2px; }

/* Footer */
.footer {
    position: relative; z-index: 1; padding: 40px 24px;
    border-top: 1px solid var(--border); text-align: center;
}
.footer-text { font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 4px; }
.footer-sub { font-size: 0.75rem; color: var(--text-muted); }

/* Responsive */
@media (max-width: 768px) {
    .nav { display: none; }
    .converter-card { padding: 28px 20px; }
    .steps-grid { grid-template-columns: 1fr; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .result-meta { gap: 16px; flex-wrap: wrap; }
    .quick-ref-table { font-size: 0.78rem; }
}
@media (max-width: 480px) {
    .hero-title { font-size: 1.8rem; }
    .result-value { font-size: 2rem; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
}