:root {
    --bg-color: #f0f4f8;
    --text-color: #1e293b;
    --glass-bg: rgba(255, 255, 255, 0.2);
    --glass-border: rgba(255, 255, 255, 0.3);
    --primary: #3b82f6;
}

[data-theme='dark'] {
    --bg-color: #0f172a;
    --text-color: #f1f5f9;
    --glass-bg: rgba(30, 41, 59, 0.4);
    --glass-border: rgba(255, 255, 255, 0.1);
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    transition: background 0.3s, color 0.3s;
}

.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    padding: 20px;
}

.app-container {
    max-width: 600px;
    margin: 40px auto;
    text-align: center;
}

header {
    display: flex;
    justify-content: space-between;
    padding: 10px 20px;
}

#timer {
    font-size: 4rem;
    font-weight: bold;
    font-family: monospace;
    padding: 30px;
}

.controls {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    gap: 10px;
    margin: 20px 0;
}

.btn {
    padding: 15px;
    border: none;
    border-radius: 10px;
    background: var(--primary);
    color: white;
    cursor: pointer;
    transition: transform 0.2s;
}

.btn:hover {
    transform: scale(1.05);
}

.btn:disabled {
    background: #64748b;
    cursor: not-allowed;
}

.lap-container {
    margin-top: 20px;
}

#lap-list {
    list-style: none;
    padding: 0;
}

#lap-list li {
    padding: 10px;
    border-bottom: 1px solid var(--glass-border);
}