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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    text-align: center;
    margin-bottom: 3rem;
    color: white;
}

header h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

header p {
    font-size: 1.2rem;
    opacity: 0.9;
    font-weight: 300;
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.timer-container {
    background: white;
    border-radius: 20px;
    padding: 3rem;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    text-align: center;
    backdrop-filter: blur(10px);
}

.timer-display {
    margin-bottom: 2rem;
}

.time {
    font-size: 5rem;
    font-weight: 700;
    color: #667eea;
    margin-bottom: 0.5rem;
    font-variant-numeric: tabular-nums;
    letter-spacing: -2px;
}

.session-info {
    font-size: 1.2rem;
    color: #666;
    font-weight: 500;
}

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

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    min-width: 100px;
}

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

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(102, 126, 234, 0.3);
}

.btn-secondary {
    background: #f8f9fa;
    color: #666;
    border: 2px solid #e9ecef;
}

.btn-secondary:hover:not(:disabled) {
    background: #e9ecef;
    transform: translateY(-1px);
}

.btn-outline {
    background: transparent;
    color: #667eea;
    border: 2px solid #667eea;
}

.btn-outline:hover,
.btn-outline.active {
    background: #667eea;
    color: white;
}

.session-controls {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.progress-container {
    margin-top: 2rem;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: #e9ecef;
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 1rem;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #667eea 0%, #764ba2 100%);
    width: 0%;
    transition: width 0.3s ease;
}

.session-count {
    font-size: 0.9rem;
    color: #666;
    font-weight: 500;
}

.settings {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
}

.settings h3 {
    margin-bottom: 1.5rem;
    color: #333;
    font-size: 1.5rem;
    font-weight: 600;
}

.setting-group {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding: 0.5rem 0;
}

.setting-group label {
    font-weight: 500;
    color: #555;
    flex: 1;
}

.setting-group input {
    width: 80px;
    padding: 0.5rem;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    text-align: center;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.setting-group input:focus {
    outline: none;
    border-color: #667eea;
}

footer {
    text-align: center;
    margin-top: 2rem;
    color: white;
    opacity: 0.8;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }
    
    header h1 {
        font-size: 2.5rem;
    }
    
    .timer-container {
        padding: 2rem 1.5rem;
    }
    
    .time {
        font-size: 3.5rem;
    }
    
    .timer-controls {
        flex-direction: column;
        align-items: center;
    }
    
    .btn {
        width: 100%;
        max-width: 200px;
    }
    
    .session-controls {
        flex-direction: column;
        align-items: center;
    }
    
    .setting-group {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }
    
    .setting-group input {
        width: 100%;
        max-width: 120px;
    }
}

/* Animation for timer completion */
@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

.timer-complete {
    animation: pulse 0.5s ease-in-out;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    body {
        background: linear-gradient(135deg, #2d3748 0%, #4a5568 100%);
    }
    
    .timer-container,
    .settings {
        background: #2d3748;
        color: white;
    }
    
    .time {
        color: #81e6d9;
    }
    
    .btn-secondary {
        background: #4a5568;
        color: white;
        border-color: #718096;
    }
    
    .btn-secondary:hover:not(:disabled) {
        background: #718096;
    }
    
    .setting-group input {
        background: #4a5568;
        color: white;
        border-color: #718096;
    }
}