/* ===== CSS Custom Properties ===== */
:root {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface-light: #334155;
    --accent: #f59e0b;
    --accent-glow: rgba(245, 158, 11, 0.4);
    --success: #10b981;
    --danger: #ef4444;
    --info: #3b82f6;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --card-bg: #1e293b;
    --card-front: linear-gradient(135deg, #6366f1, #8b5cf6);
    --card-matched: linear-gradient(135deg, #10b981, #059669);
    --radius: 12px;
    --transition: 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    overflow-x: hidden;
}

/* ===== App Container ===== */
.app {
    max-width: 900px;
    margin: 0 auto;
    padding: 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== Screens ===== */
.screen {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    flex: 1;
    text-align: center;
    animation: fadeIn 0.4s ease;
}

.screen.active {
    display: flex;
}

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

/* ===== Logo ===== */
.logo {
    width: 120px;
    height: 120px;
    margin-bottom: 1rem;
    border-radius: 20px;
    filter: drop-shadow(0 0 20px var(--accent-glow));
}

/* ===== Typography ===== */
.title {
    font-size: 2.5rem;
    font-weight: 800;
    letter-spacing: 2px;
    background: linear-gradient(135deg, var(--accent), #fbbf24);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-muted);
    font-size: 1.1rem;
    margin-bottom: 2rem;
}

/* ===== Controls ===== */
.controls-grid {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    justify-content: center;
}

.controls-grid label {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.label-text {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-muted);
}

.controls-grid select {
    background: var(--surface);
    border: 1px solid var(--surface-light);
    color: var(--text);
    padding: 0.6rem 1rem;
    border-radius: var(--radius);
    font-size: 1rem;
    cursor: pointer;
    min-width: 180px;
}

.controls-grid select:focus {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* ===== Best Time ===== */
.best-time {
    background: var(--surface);
    border: 1px solid var(--accent);
    border-radius: var(--radius);
    padding: 0.75rem 1.5rem;
    margin-bottom: 1.5rem;
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.best-time.hidden {
    display: none;
}

.best-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--accent);
}

.best-value {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--accent);
}

/* ===== Buttons ===== */
.btn {
    border: none;
    cursor: pointer;
    font-family: inherit;
    font-weight: 700;
    border-radius: var(--radius);
    transition: all var(--transition);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.btn-start {
    background: linear-gradient(135deg, var(--accent), #f97316);
    color: #000;
    font-size: 1.2rem;
    padding: 1rem 3rem;
    box-shadow: 0 4px 20px var(--accent-glow);
}

.btn-start:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 30px var(--accent-glow);
}

.btn-pause {
    background: var(--surface-light);
    color: var(--text);
    font-size: 0.9rem;
    padding: 0.4rem 0.8rem;
    line-height: 1;
}

.btn-pause:hover {
    background: var(--accent);
    color: #000;
}

.btn-resume {
    background: var(--success);
    color: #fff;
    font-size: 1rem;
    padding: 0.8rem 2rem;
}

.btn-restart {
    background: var(--info);
    color: #fff;
    font-size: 1rem;
    padding: 0.8rem 2rem;
}

.btn-quit {
    background: var(--danger);
    color: #fff;
    font-size: 1rem;
    padding: 0.8rem 2rem;
}

/* ===== HUD ===== */
.hud {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    padding: 0.75rem;
    background: var(--surface);
    border-radius: var(--radius);
    margin-bottom: 1rem;
    width: 100%;
}

.hud-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    min-width: 70px;
}

.hud-label {
    font-size: 0.6rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-muted);
}

.hud-value {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text);
}

.hud-reshuffle .hud-value {
    color: var(--accent);
}

.hud-reshuffle.warning .hud-value {
    color: var(--danger);
    animation: pulse 0.5s ease infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.4; }
}

/* ===== Speed Bonus Popup ===== */
.speed-bonus {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: var(--accent);
    color: #000;
    font-weight: 800;
    font-size: 1.3rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    z-index: 100;
    pointer-events: none;
    animation: bonusPop 0.8s ease forwards;
}

.speed-bonus.hidden {
    display: none;
}

@keyframes bonusPop {
    0% { opacity: 0; transform: translate(-50%, -50%) scale(0.5); }
    30% { opacity: 1; transform: translate(-50%, -50%) scale(1.1); }
    70% { opacity: 1; transform: translate(-50%, -60%) scale(1); }
    100% { opacity: 0; transform: translate(-50%, -80%) scale(0.9); }
}

/* ===== Reshuffle Warning ===== */
.reshuffle-warning {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: var(--danger);
    color: #fff;
    font-weight: 800;
    font-size: 1.5rem;
    padding: 1rem 2rem;
    border-radius: var(--radius);
    z-index: 100;
    pointer-events: none;
    animation: bonusPop 1s ease forwards;
}

.reshuffle-warning.hidden {
    display: none;
}

/* ===== Card Grid ===== */
.card-grid {
    display: grid;
    gap: 0.6rem;
    width: 100%;
    max-width: 700px;
    margin: 0 auto;
    padding: 0.5rem;
}

/* Grid columns set via JS inline style based on board size */

/* ===== Card ===== */
.card {
    perspective: 800px;
    aspect-ratio: 1 / 1;
    width: 100%;
    cursor: pointer;
    position: relative;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}

.card:focus-visible {
    outline: 3px solid var(--accent);
    outline-offset: 2px;
    border-radius: var(--radius);
}

.card.is-matched {
    cursor: default;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.45s ease;
    transform-style: preserve-3d;
    border-radius: var(--radius);
}

.card.is-flipped .card-inner {
    transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    inset: 0;
    backface-visibility: hidden;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Card back (shown by default - the hidden side) */
.card-back {
    background: var(--card-front);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
    position: relative;
    overflow: hidden;
    border: 2px solid rgba(139, 92, 246, 0.6);
    height: 100%;
}

/* Decorative diamond pattern on card back */
.card-back::before {
    content: '';
    position: absolute;
    inset: 8px;
    border: 2px solid rgba(255, 255, 255, 0.15);
    border-radius: 6px;
}

.card-back::after {
    content: '\2666';
    font-size: 2.5rem;
    color: rgba(255, 255, 255, 0.2);
}

/* Card front (the emoji side - revealed on flip) */
.card-front {
    background: var(--surface);
    border: 2px solid var(--surface-light);
    transform: rotateY(180deg);
    font-size: 3rem;
}

/* Matched state */
.card.is-matched .card-inner {
    transform: rotateY(180deg);
}

.card.is-matched .card-front {
    background: var(--surface);
    border-color: var(--success);
    box-shadow: 0 0 15px rgba(16, 185, 129, 0.3);
}

.card.is-matched .card-back {
    background: var(--card-matched);
}

/* Mismatch flash - brief red border, no shake */
.card.is-mismatch .card-front {
    border-color: var(--danger);
    box-shadow: 0 0 15px rgba(239, 68, 68, 0.4);
}

/* Reshuffle animation */
.card.is-shuffling .card-inner {
    animation: shuffleSpin 0.5s ease;
}

@keyframes shuffleSpin {
    0% { transform: rotateY(0deg) scale(1); }
    50% { transform: rotateY(90deg) scale(0.9); }
    100% { transform: rotateY(0deg) scale(1); }
}

/* Freeze overlay (unused - kept for reference) */

/* ===== Pause Overlay ===== */
.overlay {
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.9);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
}

.overlay.hidden {
    display: none;
}

.overlay-box {
    background: var(--surface);
    border: 1px solid var(--surface-light);
    border-radius: 20px;
    padding: 2.5rem;
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    min-width: 260px;
}

.overlay-box h2 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    color: var(--accent);
}

/* ===== End Screen ===== */
.end-title {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--success), #34d399);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 1.5rem;
}

.end-stats {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1.5rem;
    width: 100%;
    max-width: 350px;
}

.stat {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
}

.stat-label {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-muted);
}

.stat-value {
    font-size: 1.4rem;
    font-weight: 700;
}

/* Stars */
.end-stars {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    display: flex;
    gap: 0.5rem;
    justify-content: center;
}

.star {
    display: inline-block;
    transition: transform 0.3s ease;
}

.star.earned {
    animation: starPop 0.5s ease forwards;
    filter: drop-shadow(0 0 8px var(--accent-glow));
}

.star.empty {
    opacity: 0.25;
}

@keyframes starPop {
    0% { transform: scale(0); }
    60% { transform: scale(1.3); }
    100% { transform: scale(1); }
}

/* Perfect Badge */
.perfect-badge {
    background: linear-gradient(135deg, #fbbf24, #f59e0b);
    color: #000;
    font-weight: 800;
    font-size: 1.1rem;
    padding: 0.6rem 1.5rem;
    border-radius: 50px;
    margin-bottom: 1rem;
    letter-spacing: 1px;
    box-shadow: 0 0 20px var(--accent-glow);
    animation: badgePulse 1.5s ease infinite;
}

.perfect-badge.hidden {
    display: none;
}

@keyframes badgePulse {
    0%, 100% { box-shadow: 0 0 20px var(--accent-glow); }
    50% { box-shadow: 0 0 35px var(--accent-glow); }
}

/* New Best */
.new-best {
    color: var(--accent);
    font-weight: 800;
    font-size: 1.2rem;
    margin-bottom: 1rem;
    animation: badgePulse 1.5s ease infinite;
}

.new-best.hidden {
    display: none;
}

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

/* ===== Responsive ===== */
@media (max-width: 600px) {
    .title {
        font-size: 1.6rem;
    }

    .subtitle {
        font-size: 0.95rem;
    }

    .hud {
        gap: 0.4rem;
        padding: 0.5rem;
    }

    .hud-item {
        min-width: 50px;
    }

    .hud-label {
        font-size: 0.5rem;
    }

    .hud-value {
        font-size: 1rem;
    }

    .card-grid {
        gap: 0.4rem;
    }

    .card-front {
        font-size: 2.2rem;
    }

    .card-back::after {
        font-size: 1.8rem;
    }

    .end-title {
        font-size: 1.8rem;
    }

    .logo {
        width: 80px;
        height: 80px;
    }
}

@media (max-width: 400px) {
    .card-grid {
        gap: 0.3rem;
    }

    .card-front {
        font-size: 1.8rem;
    }

    .card-back::after {
        font-size: 1.4rem;
    }
}