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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 2rem;
    text-align: center;
    border-radius: 0 0 20px 20px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.subtitle {
    font-size: 1.25rem;
    opacity: 0.95;
    margin-bottom: 2rem;
}

/* Progress Summary */
.progress-summary {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 3rem;
    margin-top: 2rem;
    flex-wrap: wrap;
}

.progress-circle {
    position: relative;
}

.progress-ring {
    transform: rotate(-90deg);
}

.progress-ring-circle {
    stroke-dasharray: 326.73;
    stroke-dashoffset: 326.73;
    transition: stroke-dashoffset 0.5s ease;
    stroke-linecap: round;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}

.progress-number {
    display: block;
    font-size: 1.75rem;
    font-weight: bold;
}

.progress-label {
    display: block;
    font-size: 0.875rem;
    opacity: 0.9;
}

.progress-details {
    text-align: left;
}

.progress-details p {
    font-size: 1.125rem;
    margin-bottom: 1rem;
}

.btn-reset {
    padding: 0.6rem 1.2rem;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.4);
    border-radius: 6px;
    color: white;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-reset:hover {
    background: rgba(255, 255, 255, 0.3);
    border-color: rgba(255, 255, 255, 0.6);
}

/* How to Use Section */
.how-to-use {
    padding: 3rem 2rem;
    background: white;
    margin: 2rem 0;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.how-to-use h2 {
    text-align: center;
    color: #667eea;
    font-size: 2rem;
    margin-bottom: 2rem;
}

.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.feature {
    text-align: center;
    padding: 1.5rem;
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature h3 {
    color: #764ba2;
    margin-bottom: 0.5rem;
    font-size: 1.25rem;
}

.feature p {
    color: #666;
    font-size: 0.95rem;
}

/* Keyboard Shortcuts */
.keyboard-shortcuts {
    background: #f9fafb;
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid #e5e7eb;
}

.keyboard-shortcuts h3 {
    color: #667eea;
    margin-bottom: 1rem;
    font-size: 1.25rem;
}

.keyboard-shortcuts ul {
    list-style: none;
}

.keyboard-shortcuts li {
    padding: 0.5rem 0;
    color: #555;
}

kbd {
    background: white;
    border: 1px solid #d1d5db;
    border-radius: 4px;
    padding: 0.2rem 0.5rem;
    font-family: monospace;
    font-size: 0.9rem;
    box-shadow: 0 1px 2px rgba(0,0,0,0.1);
}

/* Lessons Section */
.lessons {
    padding: 3rem 2rem;
}

.lessons h2 {
    text-align: center;
    color: #667eea;
    font-size: 2rem;
    margin-bottom: 2rem;
}

.lessons-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

.lesson-card {
    background: white;
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    transition: all 0.3s;
    cursor: pointer;
    border: 2px solid transparent;
    text-decoration: none;
    color: inherit;
    display: block;
}

.lesson-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    border-color: #667eea;
}

.lesson-card.completed {
    border-color: #4ade80;
    background: linear-gradient(to bottom, white 0%, #f0fdf4 100%);
}

.lesson-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 0.75rem;
}

.lesson-number {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
}

.lesson-card.completed .lesson-number {
    background: #4ade80;
}

.lesson-status {
    font-size: 1.5rem;
}

.lesson-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: #333;
    margin-bottom: 0.5rem;
}

.lesson-description {
    color: #666;
    font-size: 0.9rem;
    line-height: 1.5;
}

.lesson-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #e5e7eb;
    font-size: 0.85rem;
    color: #888;
}

.lesson-attempts {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.lesson-completed-date {
    font-style: italic;
}

.loading {
    text-align: center;
    padding: 2rem;
    color: #666;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem;
    color: #666;
    font-size: 0.95rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .progress-summary {
        gap: 1.5rem;
    }

    .features {
        grid-template-columns: 1fr;
    }

    .lessons-grid {
        grid-template-columns: 1fr;
    }
}