:root{--bg-color: #0d0d12;--card-bg: rgba(255, 255, 255, .05);--accent-color: #f59e0b;--text-primary: #ffffff;--text-secondary: #94a3b8;--border-color: rgba(255, 255, 255, .1)}*{box-sizing:border-box;margin:0;padding:0}body{font-family:Inter,sans-serif;background-color:var(--bg-color);color:var(--text-primary);line-height:1.6;-webkit-font-smoothing:antialiased}h1,h2,h3,.brand{font-family:Outfit,sans-serif}.app-container{min-height:100vh;display:flex;flex-direction:column}.nav{padding:20px 40px;display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid var(--border-color);background:#0d0d12cc;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);position:sticky;top:0;z-index:100}.logo{font-size:24px;font-weight:800;color:var(--accent-color);letter-spacing:-.5px}.nav-links{display:flex;gap:32px;align-items:center}.nav-links a,.nav-links button{color:var(--text-secondary);text-decoration:none;font-size:14px;font-weight:500;transition:color .2s;background:none;border:none;cursor:pointer}.nav-links a:hover,.btn-logout:hover{color:var(--accent-color)}.dashboard{flex:1;padding:48px 40px;max-width:1200px;margin:0 auto;width:100%}.section-title{font-size:32px;margin-bottom:32px;font-weight:700}.course-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:24px}.course-card{background:var(--card-bg);border:1px solid var(--border-color);border-radius:16px;overflow:hidden;transition:transform .3s,border-color .3s;cursor:pointer}.course-card:hover{transform:translateY(-4px);border-color:var(--accent-color)}.course-thumb{width:100%;aspect-ratio:16/9;background:#1e293b;display:flex;align-items:center;justify-content:center;position:relative}.course-thumb img{width:100%;height:100%;object-fit:cover}.locked-overlay{position:absolute;inset:0;background:#0009;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px);display:flex;flex-direction:column;align-items:center;justify-content:center;color:#fff}.course-info{padding:20px}.course-info h3{font-size:18px;margin-bottom:8px}.course-meta{font-size:13px;color:var(--text-secondary)}.lesson-container{flex:1;display:flex;padding:32px 40px;gap:32px}.video-section{flex:1}.video-wrapper{width:100%;aspect-ratio:16/9;background:#000;border-radius:12px;overflow:hidden;margin-bottom:24px}.video-wrapper iframe{width:100%;height:100%;border:none}.lesson-info h1{font-size:28px;margin-bottom:12px}.tabs{display:flex;gap:24px;border-bottom:1px solid var(--border-color);margin-bottom:24px}.tab{padding:12px 0;color:var(--text-secondary);font-weight:600;cursor:pointer;border-bottom:2px solid transparent}.tab.active{color:var(--accent-color);border-bottom-color:var(--accent-color)}.interaction-section{width:380px;background:var(--card-bg);border:1px solid var(--border-color);border-radius:12px;display:flex;flex-direction:column;height:calc(100vh - 160px);position:sticky;top:100px}.interaction-header{padding:16px;border-bottom:1px solid var(--border-color);font-weight:700}.chat-box{flex:1;overflow-y:auto;padding:16px;display:flex;flex-direction:column;gap:12px}.chat-message{font-size:13px}.chat-user{font-weight:700;margin-right:8px}.chat-input-area{padding:16px;border-top:1px solid var(--border-color)}.input-box{width:100%;background:#ffffff0d;border:1px solid var(--border-color);padding:10px 16px;border-radius:8px;color:#fff;outline:none}.login-page{flex:1;display:flex;align-items:center;justify-content:center}.login-card{background:var(--card-bg);padding:48px;border-radius:24px;border:1px solid var(--border-color);width:100%;max-width:400px;text-align:center}.btn-primary{background:var(--accent-color);color:#000;padding:12px 24px;border-radius:8px;font-weight:700;border:none;cursor:pointer;width:100%;margin-top:24px}.btn-secondary{background:transparent;border:1px solid var(--border-color);color:#fff;padding:12px 24px;border-radius:8px;font-weight:600;cursor:pointer}@media(max-width:1024px){.lesson-container{flex-direction:column}.interaction-section{width:100%;height:400px;position:static}}