@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;600&display=swap');

/* ============================================================
   Design Tokens
   ============================================================ */
:root {
    --bg-deep: #05060d;
    --bg-base: #080a16;
    --bg-surface: #0f1120;
    --bg-elevated: #171a2e;
    --bg-hover: #1f2240;
    --accent-cyan: #4FC3F7;
    --accent-cyan-dim: #0277BD;
    --accent-magenta: #F06292;
    --accent-magenta-dim: #AD1457;
    --accent-green: #69F0AE;
    --accent-green-dim: #00C853;
    --accent-red: #FF5252;
    --accent-orange: #FFB74D;
    --accent-gold: #FFD740;
    --text-primary: #e8eaf6;
    --text-secondary: #7986CB;
    --text-dim: #3F51B5;
    --glass-bg: rgba(15, 17, 32, 0.75);
    --glass-border: rgba(79, 195, 247, 0.08);
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ============================================================
   Reset & Base
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
    width: 100%; height: 100%;
    font-family: 'Inter', system-ui, sans-serif;
    background: var(--bg-deep);
    color: var(--text-primary);
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
}

body { display: flex; flex-direction: column; }

button {
    font-family: inherit; cursor: pointer;
    border: none; background: none; color: inherit;
}

/* ============================================================
   Scrollbar
   ============================================================ */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--text-dim); border-radius: 3px; }

/* ============================================================
   Loading Screen
   ============================================================ */
#loading-screen {
    position: fixed; inset: 0; z-index: 1000;
    display: flex; flex-direction: column;
    align-items: center; justify-content: center;
    background: var(--bg-deep);
    transition: opacity 0.6s ease;
}
#loading-screen.hidden { opacity: 0; pointer-events: none; }
#loading-screen h1 {
    font-size: 2.5rem; font-weight: 800;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-magenta));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    margin-bottom: 1.5rem;
}
#loading-screen p { color: var(--text-secondary); margin-bottom: 2rem; font-size: 1rem; }

.loading-bar-track {
    width: 280px; height: 4px;
    background: var(--bg-elevated); border-radius: 2px; overflow: hidden;
}
.loading-bar-fill {
    height: 100%; width: 0%;
    background: linear-gradient(90deg, var(--accent-cyan), var(--accent-magenta));
    border-radius: 2px; transition: width 0.3s ease;
}

/* ============================================================
   App Layout
   ============================================================ */
#app {
    display: flex; flex-direction: column;
    width: 100%; height: 100vh;
    opacity: 0; transition: opacity 0.5s ease;
}
#app.visible { opacity: 1; }

/* ============================================================
   Top Bar
   ============================================================ */
.top-bar {
    display: flex; align-items: center; justify-content: space-between;
    padding: 0.5rem 1.2rem; height: 48px; min-height: 48px;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--glass-border);
    z-index: 100;
}
.top-bar-left { display: flex; align-items: center; gap: 1rem; }
.top-bar-right { display: flex; align-items: center; gap: 0.75rem; }

.app-logo {
    font-size: 1.1rem; font-weight: 800;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-magenta));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}

.btn-back {
    display: flex; align-items: center; gap: 0.4rem;
    padding: 0.3rem 0.7rem; border-radius: var(--radius-sm);
    font-size: 0.8rem; color: var(--text-secondary);
    transition: all var(--transition);
}
.btn-back:hover { background: var(--bg-hover); color: var(--text-primary); }

.midi-monitor {
    font-family: 'Courier New', monospace; font-size: 0.72rem;
    color: var(--accent-gold); background: rgba(255, 215, 64, 0.08);
    padding: 0.2rem 0.6rem; border-radius: 12px;
    transition: opacity 0.5s ease; white-space: nowrap;
}

.midi-status {
    display: flex; align-items: center; gap: 0.4rem;
    font-size: 0.75rem; color: var(--text-secondary);
    padding: 0.25rem 0.6rem; border-radius: 20px;
    background: var(--bg-elevated);
}
.midi-dot {
    width: 7px; height: 7px; border-radius: 50%;
    background: var(--accent-red);
    transition: background var(--transition);
}
.midi-dot.connected { background: var(--accent-green); box-shadow: 0 0 8px var(--accent-green-dim); }

/* ============================================================
   Screen Container
   ============================================================ */
.screen { display: none; flex-direction: column; flex: 1; overflow: hidden; }
.screen.active { display: flex; }

/* ============================================================
   HOME SCREEN
   ============================================================ */
.home-screen { padding: 2rem; overflow-y: auto; align-items: center; }
.home-hero {
    text-align: center; margin-bottom: 2.5rem; max-width: 640px;
}
.home-hero h2 {
    font-size: 2.4rem; font-weight: 800; margin-bottom: 0.6rem;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-magenta));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.home-hero p { color: var(--text-secondary); font-size: 1.05rem; line-height: 1.6; }

.home-actions {
    display: flex; gap: 1rem; justify-content: center;
    margin-bottom: 2.5rem; flex-wrap: wrap;
}

.btn-primary, .btn-secondary {
    padding: 0.75rem 1.8rem; border-radius: var(--radius-md);
    font-size: 0.95rem; font-weight: 600;
    transition: all var(--transition);
    position: relative; overflow: hidden;
}
.btn-primary {
    background: linear-gradient(135deg, var(--accent-cyan), #00acc1);
    color: #000; box-shadow: 0 4px 20px rgba(0, 229, 255, 0.25);
}
.btn-primary:hover {
    transform: translateY(-2px); box-shadow: 0 6px 28px rgba(0, 229, 255, 0.35);
}
.btn-secondary {
    background: var(--bg-elevated);
    border: 1px solid var(--glass-border); color: var(--text-primary);
}
.btn-secondary:hover { background: var(--bg-hover); border-color: var(--accent-cyan); }

.btn-icon {
    display: flex; align-items: center; justify-content: center;
    width: 36px; height: 36px; border-radius: var(--radius-sm);
    background: var(--bg-elevated); transition: all var(--transition);
    font-size: 1.1rem;
}
.btn-icon:hover { background: var(--bg-hover); }

/* Lesson Grid */
.section-title {
    font-size: 1.2rem; font-weight: 700; margin-bottom: 1rem;
    color: var(--text-primary); width: 100%; max-width: 900px;
}
.lesson-grid {
    display: flex; flex-direction: column; align-items: center;
    width: 100%; max-width: 900px; margin-bottom: 2rem; gap: 0.5rem;
}
.lesson-card-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 1rem; width: 100%; max-width: 900px; margin-bottom: 2rem;
}
.lesson-card {
    background: var(--bg-surface);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 1.2rem; cursor: pointer;
    transition: all var(--transition);
    position: relative; overflow: hidden;
}
.lesson-card:hover {
    border-color: var(--accent-cyan);
    transform: translateY(-3px);
    box-shadow: 0 8px 30px rgba(0, 229, 255, 0.1);
}
.lesson-card::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0;
    height: 3px; background: linear-gradient(90deg, var(--accent-cyan), var(--accent-magenta));
    opacity: 0; transition: opacity var(--transition);
}
.lesson-card:hover::before { opacity: 1; }

/* Drum card variant */
.lesson-card.drum-card::before {
    background: linear-gradient(90deg, var(--accent-magenta), var(--accent-orange));
}
.lesson-card.drum-card:hover {
    border-color: var(--accent-magenta);
    box-shadow: 0 8px 30px rgba(240, 98, 146, 0.1);
}

.lesson-card h3 { font-size: 0.95rem; font-weight: 600; margin-bottom: 0.3rem; }
.lesson-card p { font-size: 0.78rem; color: var(--text-secondary); line-height: 1.4; margin-bottom: 0.6rem; }

.difficulty-dots {
    display: flex; gap: 3px;
}
.difficulty-dots span {
    width: 8px; height: 8px; border-radius: 50%;
    background: var(--bg-hover);
}
.difficulty-dots span.filled { background: var(--accent-cyan); }

.lesson-progress-bar {
    width: 100%; height: 3px; background: var(--bg-hover);
    border-radius: 2px; margin-top: 0.6rem; overflow: hidden;
}
.lesson-progress-bar .fill {
    height: 100%; border-radius: 2px;
    background: linear-gradient(90deg, var(--accent-green), var(--accent-cyan));
    transition: width var(--transition);
}

.lesson-badge {
    position: absolute; top: 0.8rem; right: 0.8rem;
    font-size: 0.7rem; font-weight: 700;
    padding: 0.15rem 0.5rem; border-radius: 20px;
}
.lesson-badge.grade-S { background: rgba(255, 215, 0, 0.15); color: var(--accent-gold); }
.lesson-badge.grade-A { background: rgba(118, 255, 3, 0.15); color: var(--accent-green); }
.lesson-badge.grade-B { background: rgba(0, 229, 255, 0.15); color: var(--accent-cyan); }

/* Import Zone */
.import-zone {
    width: 100%; max-width: 900px;
    border: 2px dashed var(--text-dim);
    border-radius: var(--radius-md);
    padding: 2rem; text-align: center;
    transition: all var(--transition);
    cursor: pointer; margin-bottom: 2rem;
}
.import-zone:hover, .import-zone.drag-over {
    border-color: var(--accent-cyan);
    background: rgba(0, 229, 255, 0.03);
}
.import-zone p { color: var(--text-secondary); font-size: 0.9rem; }
.import-zone .icon { font-size: 2rem; margin-bottom: 0.5rem; }

/* ============================================================
   PLAY SCREEN
   ============================================================ */
.play-screen { position: relative; }

.play-area {
    flex: 1; position: relative;
    display: flex; flex-direction: column;
    background: var(--bg-base);
    overflow: hidden;
}

/* Canvas Container */
.canvas-container {
    flex: 1; position: relative; min-height: 0;
}
.canvas-container canvas {
    position: absolute; inset: 0;
    width: 100% !important; height: 100% !important;
}

/* Piano Keyboard */
.piano-keyboard {
    height: 120px; min-height: 120px;
    position: relative;
    background: linear-gradient(180deg, #0d0d15, #080810);
    border-top: 1px solid var(--glass-border);
}
.piano-keyboard-inner {
    position: relative; width: 100%; height: 100%;
    display: flex;
}
.piano-key {
    position: relative; cursor: pointer;
    transition: background 0.1s ease;
    border-radius: 0 0 4px 4px;
}
.piano-key.white {
    flex: 1;
    background: linear-gradient(180deg, #e8e8e8, #ffffff);
    border-right: 1px solid #c0c0c0;
    z-index: 1; height: 100%;
    display: flex; align-items: flex-end; justify-content: center;
    padding-bottom: 6px;
}
.piano-key.black {
    position: absolute; z-index: 2;
    height: 62%; top: 0;
    background: linear-gradient(180deg, #1a1a1a, #333);
    border-radius: 0 0 4px 4px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.5);
}

/* Key States */
.piano-key.key-played.white { background: linear-gradient(180deg, #b0e0e6, #c5f0f5); }
.piano-key.key-played.black { background: linear-gradient(180deg, #005060, #007080); }

.piano-key.key-correct.white {
    background: linear-gradient(180deg, #a0ff50, #76FF03) !important;
    box-shadow: 0 0 20px rgba(118, 255, 3, calc(var(--glow-intensity, 0.7)));
}
.piano-key.key-correct.black {
    background: linear-gradient(180deg, #3a8000, #76FF03) !important;
    box-shadow: 0 0 20px rgba(118, 255, 3, calc(var(--glow-intensity, 0.7)));
}
.piano-key.key-wrong.white {
    background: linear-gradient(180deg, #ff6070, #FF1744) !important;
    box-shadow: 0 0 20px rgba(255, 23, 68, 0.6);
}
.piano-key.key-wrong.black {
    background: linear-gradient(180deg, #8b0020, #FF1744) !important;
}
.piano-key.key-expected.white {
    background: linear-gradient(180deg, #d0f0ff, #90e0ff);
    animation: pulse-expected 1.2s ease infinite;
}
.piano-key.key-expected.black {
    background: linear-gradient(180deg, #003050, #005080);
    animation: pulse-expected 1.2s ease infinite;
}

@keyframes pulse-expected {
    0%, 100% { box-shadow: 0 0 8px rgba(0, 229, 255, 0.3); }
    50% { box-shadow: 0 0 20px rgba(0, 229, 255, 0.6); }
}

.key-shake { animation: shake 0.35s ease; }
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-3px); }
    75% { transform: translateX(3px); }
}

.key-label {
    font-size: 0.55rem; font-weight: 600; color: #888;
    font-family: 'JetBrains Mono', monospace;
    user-select: none; pointer-events: none;
}

/* ============================================================
   Controls Bar
   ============================================================ */
.controls-bar {
    display: flex; align-items: center; justify-content: space-between;
    padding: 0.4rem 1rem; height: 44px;
    background: var(--bg-surface);
    border-top: 1px solid var(--glass-border);
    gap: 1rem;
}
.controls-left, .controls-center, .controls-right {
    display: flex; align-items: center; gap: 0.6rem;
}
.controls-center { flex: 1; justify-content: center; }

.btn-control {
    display: flex; align-items: center; justify-content: center;
    width: 34px; height: 34px; border-radius: var(--radius-sm);
    background: var(--bg-elevated); transition: all var(--transition);
    font-size: 1rem;
}
.btn-control:hover { background: var(--bg-hover); }
.btn-control.active { background: var(--accent-cyan); color: #000; }

.tempo-control {
    display: flex; align-items: center; gap: 0.4rem;
    font-size: 0.75rem; color: var(--text-secondary);
}
.tempo-control input[type="range"] {
    width: 80px; accent-color: var(--accent-cyan);
}
.tempo-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem; min-width: 35px; text-align: center;
    color: var(--accent-cyan);
}

.time-display {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem; color: var(--text-secondary);
}

/* ============================================================
   Score Overlay
   ============================================================ */
.score-overlay {
    position: absolute; top: 0.75rem; right: 0.75rem;
    display: flex; flex-direction: column; align-items: flex-end; gap: 0.4rem;
    z-index: 50; pointer-events: none;
}
.score-box {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 0.6rem 1rem;
    text-align: right;
}
.score-value {
    font-size: 1.6rem; font-weight: 800;
    font-family: 'JetBrains Mono', monospace;
    background: linear-gradient(135deg, var(--accent-cyan), var(--accent-magenta));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.score-label { font-size: 0.65rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: 1px; }

.streak-box {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-sm);
    padding: 0.3rem 0.7rem;
    font-size: 0.8rem; font-weight: 700;
    color: var(--accent-orange);
}

.chord-display {
    position: absolute; top: 0.75rem; left: 0.75rem;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 0.5rem 1rem; z-index: 50;
    pointer-events: none;
}
.chord-display .chord-name {
    font-size: 1.4rem; font-weight: 800;
    font-family: 'JetBrains Mono', monospace;
    color: var(--accent-cyan);
}
.chord-display .chord-label {
    font-size: 0.6rem; color: var(--text-dim);
    text-transform: uppercase; letter-spacing: 1px;
}

/* ============================================================
   Lesson Info Panel (in play screen header)
   ============================================================ */
.lesson-header {
    font-size: 0.85rem; font-weight: 600;
    color: var(--text-primary); max-width: 300px;
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}

/* ============================================================
   Results Modal
   ============================================================ */
.modal-backdrop {
    position: fixed; inset: 0; z-index: 500;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(8px);
    display: flex; align-items: center; justify-content: center;
    opacity: 0; pointer-events: none;
    transition: opacity 0.3s ease;
}
.modal-backdrop.visible { opacity: 1; pointer-events: all; }

.results-modal {
    background: var(--bg-surface);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    padding: 2.5rem; max-width: 420px; width: 90%;
    text-align: center;
    transform: translateY(20px); transition: transform 0.3s ease;
}
.modal-backdrop.visible .results-modal { transform: translateY(0); }

.results-grade {
    font-size: 4rem; font-weight: 800;
    margin-bottom: 0.5rem;
}
.results-score {
    font-size: 1.5rem; font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    color: var(--text-primary); margin-bottom: 1.5rem;
}
.results-stats {
    display: grid; grid-template-columns: 1fr 1fr 1fr;
    gap: 1rem; margin-bottom: 2rem;
}
.results-stat {
    text-align: center;
}
.results-stat .value {
    font-size: 1.3rem; font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
}
.results-stat .label {
    font-size: 0.65rem; color: var(--text-dim);
    text-transform: uppercase; letter-spacing: 1px;
}
.results-actions { display: flex; gap: 0.75rem; justify-content: center; }

/* ============================================================
   Tips Panel
   ============================================================ */
.tips-panel {
    position: absolute; bottom: 50px; left: 0.75rem;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 0.6rem 1rem; max-width: 300px;
    z-index: 50; font-size: 0.75rem;
    color: var(--text-secondary); line-height: 1.5;
    transition: opacity 0.3s ease;
}
.tips-panel .tip-title {
    font-size: 0.65rem; font-weight: 700; color: var(--accent-cyan);
    text-transform: uppercase; letter-spacing: 1px; margin-bottom: 0.3rem;
}
.tips-panel ul { list-style: none; }
.tips-panel li::before { content: '→ '; color: var(--accent-cyan); }

/* ============================================================
   Waiting Indicator
   ============================================================ */
.waiting-indicator {
    position: absolute; left: 50%; bottom: 130px;
    transform: translateX(-50%);
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(0, 229, 255, 0.3);
    border-radius: var(--radius-xl);
    padding: 0.4rem 1.2rem;
    font-size: 0.8rem; font-weight: 600;
    color: var(--accent-cyan);
    opacity: 0; pointer-events: none;
    transition: opacity 0.2s ease;
    z-index: 50;
    animation: pulse-waiting 1.5s ease infinite;
}
.waiting-indicator.visible { opacity: 1; }

@keyframes pulse-waiting {
    0%, 100% { box-shadow: 0 0 10px rgba(0, 229, 255, 0.2); }
    50% { box-shadow: 0 0 25px rgba(0, 229, 255, 0.4); }
}

/* ============================================================
   Countdown Display
   ============================================================ */
.countdown-display {
    position: absolute;
    left: 50%; top: 40%;
    transform: translate(-50%, -50%);
    font-size: 5rem; font-weight: 800;
    font-family: 'JetBrains Mono', monospace;
    color: var(--accent-cyan);
    text-shadow: 0 0 40px rgba(0, 229, 255, 0.5), 0 0 80px rgba(0, 229, 255, 0.2);
    z-index: 60; pointer-events: none;
    animation: countdown-pulse 1s ease infinite;
}

@keyframes countdown-pulse {
    0% { transform: translate(-50%, -50%) scale(1.2); opacity: 0.3; }
    20% { transform: translate(-50%, -50%) scale(1); opacity: 1; }
    100% { transform: translate(-50%, -50%) scale(0.9); opacity: 0.6; }
}

/* ============================================================
   Shortcut Hints
   ============================================================ */
.shortcut-hint {
    font-size: 0.65rem;
    color: var(--text-dim);
    font-family: 'JetBrains Mono', monospace;
    letter-spacing: 0.5px;
}