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

:root {
    --primary-color: #6366f1;
    --secondary-color: #8b5cf6;
    --bg-color: #0f172a;
    --surface-color: #1e293b;
    --text-color: #f1f5f9;
    --text-secondary: #94a3b8;
    --success-color: #10b981;
    --danger-color: #ef4444;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: linear-gradient(135deg, var(--bg-color) 0%, #1e293b 100%);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: var(--surface-color);
    border-radius: 24px;
    padding: 48px 40px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    max-width: 500px;
    width: 100%;
}

h1 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 32px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.timer-display {
    font-size: 5rem;
    font-weight: 700;
    text-align: center;
    margin: 32px 0;
    font-variant-numeric: tabular-nums;
    letter-spacing: 0.05em;
    color: var(--text-color);
    text-shadow: 0 0 20px rgba(99, 102, 241, 0.3);
}

.controls {
    display: flex;
    gap: 12px;
    margin-bottom: 40px;
}

.btn {
    flex: 1;
    padding: 16px 24px;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(99, 102, 241, 0.4);
}

.btn-secondary {
    background: var(--bg-color);
    color: var(--text-color);
}

.btn-secondary:hover:not(:disabled) {
    background: #334155;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.presets, .custom-time {
    margin-top: 32px;
}

h3 {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.preset-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

.preset-btn {
    padding: 12px 16px;
    background: var(--bg-color);
    border: 2px solid transparent;
    border-radius: 8px;
    color: var(--text-color);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.preset-btn:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.time-inputs {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 16px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.input-group label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.input-group input {
    padding: 12px 16px;
    background: var(--bg-color);
    border: 2px solid transparent;
    border-radius: 8px;
    color: var(--text-color);
    font-size: 1.125rem;
    font-weight: 600;
    transition: all 0.2s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

#setCustomBtn {
    width: 100%;
}

.timer-display.running {
    color: var(--success-color);
    text-shadow: 0 0 20px rgba(16, 185, 129, 0.3);
}

.timer-display.finished {
    color: var(--danger-color);
    text-shadow: 0 0 20px rgba(239, 68, 68, 0.3);
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
}

@media (max-width: 640px) {
    .container {
        padding: 32px 24px;
    }

    h1 {
        font-size: 2rem;
    }

    .timer-display {
        font-size: 3.5rem;
    }

    .preset-buttons {
        grid-template-columns: repeat(2, 1fr);
    }
}