/* Custom Styles & Modern Aesthetic Enhancements */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Noto+Sans+HK:wght@300;400;500;700&display=swap');

:root {
    --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
    --font-cantonese: 'Noto Sans HK', 'PingFang HK', 'Microsoft JhengHei', 'HK Grotesk', sans-serif;
}

body {
    font-family: var(--font-sans);
    background-color: #0f172a;
    color: #f8fafc;
    min-height: 100vh;
}

.font-cantonese {
    font-family: var(--font-cantonese);
}

/* Glassmorphism effects */
.glass-card {
    background: rgba(30, 41, 59, 0.7);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid rgba(255, 255, 255, 0.08);
}

.glass-card-hover {
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.glass-card-hover:hover {
    transform: translateY(-4px);
    background: rgba(30, 41, 59, 0.85);
    border-color: rgba(56, 189, 248, 0.3);
    box-shadow: 0 20px 30px -10px rgba(0, 0, 0, 0.5), 0 0 15px rgba(56, 189, 248, 0.15);
}

.glass-modal {
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid rgba(255, 255, 255, 0.12);
}

/* 3D Flashcard Flip Engine */
.flip-card-perspective {
    perspective: 1000px;
}

.flip-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    transform-style: preserve-3d;
}

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

.flip-card-front,
.flip-card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    top: 0;
    left: 0;
}

.flip-card-back {
    transform: rotateY(180deg);
}

/* Soundwave Animation for Audio Playback */
@keyframes soundwave-bar {
    0%, 100% { height: 4px; }
    50% { height: 18px; }
}

.soundwave-playing span {
    display: inline-block;
    width: 3px;
    background-color: #38bdf8;
    border-radius: 9999px;
    margin: 0 1.5px;
    animation: soundwave-bar 0.8s ease-in-out infinite;
}

.soundwave-playing span:nth-child(1) { animation-delay: 0.0s; }
.soundwave-playing span:nth-child(2) { animation-delay: 0.2s; }
.soundwave-playing span:nth-child(3) { animation-delay: 0.4s; }
.soundwave-playing span:nth-child(4) { animation-delay: 0.1s; }

/* Custom Scrollbars */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: rgba(15, 23, 42, 0.6);
}

::-webkit-scrollbar-thumb {
    background: rgba(100, 116, 139, 0.4);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(148, 163, 184, 0.6);
}

/* Jyutping Badge Styling */
.jyutping-badge {
    background: linear-gradient(135deg, rgba(56, 189, 248, 0.15), rgba(129, 140, 248, 0.15));
    color: #38bdf8;
    border: 1px solid rgba(56, 189, 248, 0.3);
}

/* Tone Color Indicators */
.tone-1 { color: #f43f5e; } /* High flat */
.tone-2 { color: #fb923c; } /* Rising */
.tone-3 { color: #facc15; } /* Mid flat */
.tone-4 { color: #4ade80; } /* Low falling */
.tone-5 { color: #38bdf8; } /* Low rising */
.tone-6 { color: #c084fc; } /* Low flat */

/* Pulse glow keyframes */
@keyframes soft-pulse {
    0%, 100% { opacity: 0.6; transform: scale(1); }
    50% { opacity: 1; transform: scale(1.05); }
}

.pulse-glow {
    animation: soft-pulse 3s infinite ease-in-out;
}