:root {
    --primary-color: #2196f3;
    --stop-color: #ff4081;
    --background: #1a1a1a;
}

body {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    margin: 0;
    background: var(--background);
    font-family: 'Segoe UI', sans-serif;
}

.timer-container {
    background: #2d2d2d;
    padding: 2rem 4rem;
    border-radius: 20px;
    box-shadow: 0 0 30px rgba(33, 150, 243, 0.2);
    position: relative;
    overflow: hidden;
}

.timer-display {
    font-size: 3.5rem;
    color: var(--primary-color);
    text-shadow: 0 0 10px rgba(33, 150, 243, 0.5);
    font-family: 'Fira Code', monospace;
    letter-spacing: 3px;
    margin: 1rem 0;
    text-align: center;
    transition: transform 0.1s ease;
}

.controls {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
    justify-content: center;
}

.btn {
    padding: 12px 28px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
    min-width: 120px;
}

.toggle-btn {
    background: var(--primary-color);
    color: white;
    position: relative;
    overflow: hidden;
}

.toggle-btn.stop-mode {
    background: var(--stop-color);
}

.reset-btn {
    background: #666;
    color: white;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

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

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