:root {
     --bg-primary: #1e1e1e;
     --bg-secondary: #252526;
     --bg-tertiary: #2d2d30;
     --bg-hover: #2a2d2e;
     --border: #3e3e42;
     --text-primary: #cccccc;
     --text-secondary: #858585;
     --accent-blue: #0098ff;
     --accent-green: #4ec9b0;
     --accent-purple: #c586c0;
     --accent-orange: #ce9178;
     --status-success: #89d185;
     --status-locked: #858585;
     --shadow: rgba(0, 0, 0, 0.35);
}
 * {
     box-sizing: border-box;
     margin: 0;
     padding: 0;
}
 body {
     font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
     background: var(--bg-primary);
     color: var(--text-primary);
     line-height: 1.6;
     min-height: 100vh;
}
 .topbar {
     background: var(--bg-secondary);
     border-bottom: 1px solid var(--border);
     padding: 0 24px;
     height: 48px;
     display: flex;
     align-items: center;
     gap: 16px;
     position: sticky;
     top: 0;
     z-index: 100;
}
 .topbar-logo {
     display: flex;
     align-items: center;
     gap: 8px;
     font-weight: 600;
     font-size: 14px;
}
 .topbar-logo svg {
     width: 20px;
     height: 20px;
     fill: var(--accent-blue);
}
 .topbar-title {
     color: var(--text-secondary);
     font-size: 13px;
     margin-left: auto;
}
 .container {
     max-width: 1400px;
     margin: 0 auto;
     padding: 32px 24px;
}
 .welcome-panel {
     background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
     border: 1px solid var(--border);
     border-radius: 12px;
     padding: 48px;
     max-width: 600px;
     margin: 60px auto 40px;
     box-shadow: 0 4px 16px var(--shadow);
     position: relative;
     overflow: hidden;
}
 .markdown-content {
     background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
     border: 1px solid var(--border);
     border-radius: 12px;
     padding: 0 48px 48px 48px;
     width: 900px;
     margin: 60px auto 40px;
     box-shadow: 0 4px 16px var(--shadow);
     position: relative;
     overflow: hidden;
}
 .welcome-panel::before {
     content: '';
     position: absolute;
     top: 0;
     right: 0;
     width: 300px;
     height: 300px;
     background: radial-gradient(circle, rgba(0, 152, 255, 0.1) 0%, transparent 70%);
     pointer-events: none;
}
 .welcome-panel h1 {
     font-size: 32px;
     font-weight: 700;
     margin-bottom: 8px;
     background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-blue) 100%);
     -webkit-background-clip: text;
     -webkit-text-fill-color: transparent;
     background-clip: text;
}
 .welcome-panel p {
     color: var(--text-secondary);
     font-size: 14px;
     margin-bottom: 32px;
}
 .input-group {
     display: flex;
     gap: 12px;
     margin-bottom: 24px;
}
 .input-group input {
     flex: 1;
     background: var(--bg-primary);
     border: 1px solid var(--border);
     color: var(--text-primary);
     padding: 10px 16px;
     font-size: 14px;
     border-radius: 4px;
     outline: none;
     transition: border-color 0.2s;
}
 .input-group input:focus {
     border-color: var(--accent-blue);
}
 .btn {
     background: var(--accent-blue);
     color: white;
     border: none;
     padding: 10px 24px;
     font-size: 14px;
     font-weight: 500;
     border-radius: 4px;
     cursor: pointer;
     transition: all 0.2s;
     white-space: nowrap;
}
 .btn:hover {
     background: #007acc;
     transform: translateY(-1px);
}
 .btn-secondary {
     background: transparent;
     border: 1px solid var(--border);
     color: var(--text-primary);
}
 .btn-secondary:hover {
     background: var(--bg-hover);
     border-color: var(--text-secondary);
}
 .courses-header {
     display: flex;
     justify-content: space-between;
     align-items: center;
     margin-bottom: 24px;
     padding-bottom: 16px;
     border-bottom: 1px solid var(--border);
}
 .courses-header h2 {
     font-size: 20px;
     font-weight: 600;
}
 .course-grid {
     display: grid;
     grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
     gap: 20px;
     margin-bottom: 24px;
}
 .course-card {
     background: var(--bg-secondary);
     border: 1px solid var(--border);
     border-radius: 12px;
     padding: 24px;
     transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
     cursor: pointer;
     position: relative;
     overflow: hidden;
}
 .course-card::before {
     content: '';
     position: absolute;
     top: 0;
     left: 0;
     width: 4px;
     height: 100%;
     background: linear-gradient(180deg, var(--accent-blue), var(--accent-green));
     transform: scaleY(0);
     transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}
 .course-card:hover {
     border-color: var(--accent-blue);
     background: var(--bg-hover);
     transform: translateX(4px);
     box-shadow: 0 8px 24px var(--shadow);
}
 .course-card:hover::before {
     transform: scaleY(1);
}
 .course-card-header {
     display: flex;
     align-items: start;
     gap: 12px;
     margin-bottom: 16px;
}
 .course-icon {
     width: 40px;
     height: 40px;
     background: var(--bg-tertiary);
     border-radius: 6px;
     display: flex;
     align-items: center;
     justify-content: center;
     flex-shrink: 0;
}
 .course-icon svg {
     width: 20px;
     height: 20px;
     fill: var(--accent-green);
}
 .course-info h3 {
     font-size: 16px;
     font-weight: 600;
     margin-bottom: 4px;
}
 .course-tag {
     display: inline-block;
     background: var(--bg-tertiary);
     color: var(--accent-purple);
     padding: 2px 8px;
     border-radius: 4px;
     font-size: 12px;
     font-weight: 500;
}
 .course-card-footer {
     display: flex;
     justify-content: space-between;
     align-items: center;
     margin-top: 20px;
     padding-top: 16px;
     border-top: 1px solid var(--border);
}
 .course-link {
     color: var(--accent-blue);
     text-decoration: none;
     font-size: 13px;
     font-weight: 500;
     display: flex;
     align-items: center;
     gap: 6px;
     transition: gap 0.2s;
}
 .course-link:hover {
     gap: 10px;
}
 .course-header {
     background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
     border: 1px solid var(--border);
     border-radius: 12px;
     padding: 40px;
     margin-bottom: 32px;
     position: relative;
     overflow: hidden;
}
 .course-header::before {
     content: '';
     position: absolute;
     top: 0;
     right: 0;
     width: 300px;
     height: 300px;
     background: radial-gradient(circle, rgba(0, 152, 255, 0.1) 0%, transparent 70%);
     pointer-events: none;
}
 .back-link {
     display: inline-flex;
     align-items: center;
     gap: 8px;
     color: var(--text-secondary);
     text-decoration: none;
     font-size: 13px;
     margin-bottom: 24px;
     transition: all 0.2s;
     padding: 8px 12px;
     border-radius: 6px;
}
 .back-link:hover {
     color: var(--accent-blue);
     background: rgba(0, 152, 255, 0.1);
     transform: translateX(-4px);
}
 .course-title {
     font-size: 32px;
     font-weight: 700;
     margin-bottom: 12px;
     background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-blue) 100%);
     -webkit-background-clip: text;
     -webkit-text-fill-color: transparent;
     background-clip: text;
}
 .course-subtitle {
     display: inline-block;
     background: var(--bg-tertiary);
     color: var(--accent-purple);
     padding: 2px 8px;
     border-radius: 4px;
     font-size: 12px;
     font-weight: 500;
}
 .lessons-container {
     display: flex;
     flex-direction: column;
     gap: 16px;
}
 .lesson-card {
     background: var(--bg-secondary);
     border: 1px solid var(--border);
     border-radius: 12px;
     padding: 24px 28px;
     transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
     position: relative;
     overflow: hidden;
}
 .lesson-card::before {
     content: '';
     position: absolute;
     left: 0;
     top: 0;
     width: 4px;
     height: 100%;
     background: linear-gradient(180deg, var(--accent-blue), var(--accent-green));
     transform: scaleY(0);
     transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}
 .lesson-card:not(.locked):hover {
     border-color: var(--accent-blue);
     background: var(--bg-hover);
     transform: translateX(4px);
     box-shadow: 0 8px 24px var(--shadow);
}
 .lesson-card:not(.locked):hover::before {
     transform: scaleY(1);
}
 .lesson-card.locked {
     opacity: 0.6;
     background: linear-gradient(135deg, var(--bg-secondary) 0%, rgba(45, 45, 48, 0.5) 100%);
}
 .lesson-header {
     display: flex;
     justify-content: space-between;
     align-items: start;
     margin-bottom: 16px;
     gap: 16px;
}
 .lesson-title {
     font-size: 18px;
     font-weight: 600;
     margin-bottom: 8px;
     color: var(--text-primary);
}
 .lesson-meta {
     display: flex;
     align-items: center;
     gap: 20px;
     color: var(--text-secondary);
     font-size: 13px;
     flex-wrap: wrap;
}
 .lesson-meta-item {
     display: flex;
     align-items: center;
     gap: 6px;
     background: var(--bg-tertiary);
     padding: 4px 10px;
     border-radius: 6px;
}
 .lesson-desc {
     color: var(--text-secondary);
     font-size: 14px;
     line-height: 1.8;
     margin-bottom: 20px;
}
 .lesson-attachments {
     display: flex;
     flex-wrap: wrap;
     gap: 10px;
     padding-top: 16px;
     border-top: 1px solid var(--border);
}
 .attachment-link {
     display: inline-flex;
     align-items: center;
     gap: 8px;
     padding: 8px 16px;
     background: linear-gradient(135deg, var(--bg-tertiary) 0%, var(--bg-hover) 100%);
     border: 1px solid var(--border);
     border-radius: 8px;
     color: var(--accent-orange);
     text-decoration: none;
     font-size: 13px;
     font-weight: 500;
     transition: all 0.2s;
}
 .attachment-link:hover {
     background: var(--bg-hover);
     border-color: var(--accent-orange);
     transform: translateY(-2px);
     box-shadow: 0 4px 12px rgba(206, 145, 120, 0.2);
}
 .empty-state {
     text-align: center;
     padding: 60px 24px;
     color: var(--text-secondary);
}
 .empty-state svg {
     width: 64px;
     height: 64px;
     fill: var(--text-secondary);
     opacity: 0.5;
     margin-bottom: 16px;
}
 .status-badge {
     display: inline-flex;
     align-items: center;
     gap: 6px;
     padding: 6px 14px;
     border-radius: 20px;
     font-size: 12px;
     font-weight: 600;
     text-transform: uppercase;
     letter-spacing: 0.5px;
     flex-shrink: 0;
}
 .status-badge.unlocked {
     background: linear-gradient(135deg, rgba(137, 209, 133, 0.2), rgba(78, 201, 176, 0.2));
     color: var(--status-success);
     border: 1px solid rgba(137, 209, 133, 0.3);
}
 .status-badge.locked {
     background: rgba(133, 133, 133, 0.15);
     color: var(--status-locked);
     border: 1px solid rgba(133, 133, 133, 0.2);
}
 @media (max-width: 768px) {
     .container {
         padding: 16px;
    }
     .welcome-panel {
         padding: 32px 24px;
         margin: 24px auto;
    }
     .course-grid {
         grid-template-columns: 1fr;
    }
     .input-group {
         flex-direction: column;
    }
}
 .normal {
     color: #858585;
     text-decoration: none;
}
 .normal:hover {
     text-decoration: none;
     color: #cccccc;
}
 .morenormal {
     color: #cccccc;
     text-decoration: none;
}
 .morenormal:hover {
     text-decoration: none;
}