:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #f1f5f9;
    --accent-color: #10b981;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --background: #ffffff;
    --card-bg: #f8fafc;
    --border-color: #e2e8f0;
    --shadow-light: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-medium: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-large: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --border-radius: 16px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    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: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 2rem;
}

header {
    text-align: center;
    color: white;
}

.logo {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
}

.logo i {
    color: #fbbf24;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

.tagline {
    font-size: 1.1rem;
    opacity: 0.9;
    font-weight: 300;
}

main {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    align-items: center;
}

.activity-card {
    background: var(--background);
    border-radius: var(--border-radius);
    padding: 3rem 2rem;
    text-align: center;
    box-shadow: var(--shadow-large);
    width: 100%;
    max-width: 500px;
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.activity-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.activity-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 80px;
    height: 80px;
    background: var(--secondary-color);
    border-radius: 50%;
    margin: 0 auto 1.5rem;
    transition: var(--transition);
}

.activity-title {
    font-size: 1.75rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.activity-description {
    font-size: 1.1rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 1.5rem;
}

.activity-timer {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--accent-color);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 50px;
    font-weight: 500;
    font-size: 0.9rem;
}

.shuffle-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2.5rem;
    border-radius: 50px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-medium);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 220px;
    justify-content: center;
}

.shuffle-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-large);
}

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

.shuffle-btn.loading {
    pointer-events: none;
    opacity: 0.8;
}

.shuffle-btn.loading i {
    animation: spin 1s linear infinite;
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.stats {
    display: flex;
    gap: 3rem;
    justify-content: center;
    flex-wrap: wrap;
}

.stat-item {
    text-align: center;
    color: white;
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: #fbbf24;
}

.stat-label {
    font-size: 0.9rem;
    opacity: 0.9;
    font-weight: 400;
}

footer {
    text-align: center;
    color: white;
    opacity: 0.8;
    font-size: 0.9rem;
    margin-top: auto;
}

/* Category-specific styling */
.brain-teaser .activity-icon {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
}

.stretch .activity-icon {
    background: linear-gradient(135deg, #f093fb, #f5576c);
    color: white;
}

.quote .activity-icon {
    background: linear-gradient(135deg, #4facfe, #00f2fe);
    color: white;
}

.drawing .activity-icon {
    background: linear-gradient(135deg, #43e97b, #38f9d7);
    color: white;
}

.breathing .activity-icon {
    background: linear-gradient(135deg, #fa709a, #fee140);
    color: white;
}

/* Responsive design */
@media (max-width: 640px) {
    .container {
        padding: 1rem;
    }
    
    .logo {
        font-size: 2rem;
    }
    
    .activity-card {
        padding: 2rem 1.5rem;
    }
    
    .activity-title {
        font-size: 1.5rem;
    }
    
    .activity-description {
        font-size: 1rem;
    }
    
    .shuffle-btn {
        padding: 0.875rem 2rem;
        font-size: 1rem;
        min-width: 200px;
    }
    
    .stats {
        gap: 2rem;
    }
}

/* Animation for activity transitions */
.activity-card.updating {
    opacity: 0.7;
    transform: scale(0.98);
}

.fade-in {
    animation: fadeIn 0.5s ease-out forwards;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}