:root {
    --bg-color: #451a03;
    --card-bg: rgba(69, 26, 3, 0.7);
    --text-primary: #fff7ed;
    --text-secondary: #fed7aa;
    --accent-primary: #f59e0b;
    --accent-secondary: #d97706;
    --success: #10b981;
    --error: #f87171;
    --glass-border: rgba(254, 215, 170, 0.2);
    --font-main: 'Outfit', sans-serif;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-main);
    min-height: 100vh;
    min-height: 100dvh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-image:
        radial-gradient(circle at 10% 20%, rgba(245, 158, 11, 0.15) 0%, transparent 40%),
        radial-gradient(circle at 90% 80%, rgba(217, 119, 6, 0.15) 0%, transparent 40%);
    padding: 1rem;
}

.app-container {
    width: 100%;
    max-width: 650px;
    padding: 2rem;
    text-align: center;
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

header h1 {
    font-weight: 600;
    font-size: 2.5rem;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

header p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    text-transform: uppercase;
    font-size: 0.9rem;
    letter-spacing: 1px;
}

.primary-btn {
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    border: none;
    padding: 1rem 3rem;
    border-radius: 50px;
    color: white;
    font-weight: 600;
    font-size: 1.1rem;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    font-family: var(--font-main);
}

.primary-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px -5px rgba(245, 158, 11, 0.5);
}

.secondary-btn {
    background: transparent;
    border: 1px solid var(--glass-border);
    color: var(--text-secondary);
    padding: 0.5rem 1rem;
    border-radius: 50px;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
    font-family: var(--font-main);
    text-decoration: none;
    display: inline-block;
}

.secondary-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.05);
}

.nav-back-button {
    margin-top: 1.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.2s;
    padding: 0.8rem 1.5rem;
    border: 1px solid var(--glass-border);
    border-radius: 50px;
    background: rgba(255, 255, 255, 0.05);
    display: inline-block;
}

.nav-back-button:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

#start-menu {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
}

#score-board {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 2rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.streak-label {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--accent-primary);
}

.reference-link {
    font-size: 0.9rem;
    color: var(--accent-primary);
    text-decoration: none;
    padding: 0.8rem 1.2rem;
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.05);
    transition: all 0.2s;
    max-width: 90%;
    line-height: 1.4;
}

.reference-link:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.hidden {
    display: none !important;
}

.feedback-container {
    margin-bottom: 1.5rem;
    min-height: 80px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

#feedback-message {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.control-buttons {
    display: flex;
    justify-content: center;
    gap: 0.8rem;
    margin-top: 0.5rem;
}

.play-btn {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    color: var(--text-primary);
    padding: 0.6rem 1rem;
    border-radius: 12px;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    font-family: var(--font-main);
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 100px;
}

.play-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.play-btn:active {
    transform: translateY(0);
}

/* Piano Styles */
.piano-outer {
    margin-bottom: 2rem;
    padding: 10px;
    background: #451a03;
    border-radius: 12px;
    box-shadow: inset 0 2px 10px rgba(0, 0, 0, 0.5);
}

.piano-container {
    position: relative;
    width: 100%;
    height: 120px;
    display: flex;
    justify-content: flex-start;
}

.white-key {
    background: #f8fafc;
    flex: 1;
    height: 100%;
    border-radius: 0 0 4px 4px;
    position: relative;
    z-index: 1;
    box-shadow: 0 3px 0 #cbd5e1;
    border-right: 1px solid #e2e8f0;
    cursor: pointer;
    display: flex;
    align-items: flex-end;
    justify-content: center;
    padding-bottom: 10px;
    color: #475569;
    font-weight: 600;
    user-select: none;
}

.white-key.active {
    background: var(--accent-primary);
    box-shadow: 0 1px 0 #cbd5e1;
    transform: translateY(2px);
    color: white;
}

.black-key {
    background: #240c02;
    width: 8%;
    height: 60%;
    position: absolute;
    top: 0;
    z-index: 2;
    border-radius: 0 0 4px 4px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
    pointer-events: none;
}

.black-key.active {
    background: var(--accent-secondary);
    transform: translateY(2px);
}

/* Choices Styles */
.choices-container {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.8rem;
    margin-top: 1rem;
}

.choice-btn {
    background: rgba(69, 26, 3, 0.5);
    border: 1px solid var(--glass-border);
    color: var(--text-primary);
    padding: 0.8rem 0.5rem;
    border-radius: 12px;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    font-family: var(--font-main);
}

.choice-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.choice-btn.correct {
    background: var(--success);
    color: #451a03;
    border-color: var(--success);
}

.choice-btn.wrong {
    background: var(--error);
    color: white;
    border-color: var(--error);
}

footer {
    margin-top: 2rem;
    font-size: 0.8rem;
    color: var(--text-secondary);
    opacity: 0.6;
}

@media (max-width: 480px) {
    .choices-container {
        grid-template-columns: repeat(2, 1fr);
    }

    header h1 {
        font-size: 2rem;
    }
}