:root{--bg-dark: #1a1a2e;--bg-light: #f5f5f5;--text-dark: #eee;--text-light: #333;--accent: #4a90d9;--accent-hover: #357abd;--card-dark: #16213e;--card-light: #fff;--sidebar-width: 250px}*{box-sizing:border-box;margin:0;padding:0}html,body{margin:0;padding:0;font-family:Inter,Segoe UI,sans-serif;line-height:1.6;background:linear-gradient(135deg,#1a1a2e,#16213e);color:#e0e0e0;min-height:100vh;transition:background-color .3s,color .3s}body.dark{background-color:var(--bg-dark);color:var(--text-dark)}body.light{background-color:var(--bg-light);color:var(--text-light)}.header{display:flex;align-items:center;justify-content:space-between;padding:1rem 2rem;background:linear-gradient(135deg,var(--accent),#2c3e50);color:#fff;position:fixed;top:0;left:0;right:0;z-index:100;height:60px}.header .logo{font-size:1.5rem;font-weight:700}.header button{background:transparent;border:none;color:#fff;font-size:1.5rem;cursor:pointer;padding:.5rem;border-radius:4px;transition:background .2s}.header button:hover{background:#fff3}.sidebar{position:fixed;top:60px;left:0;width:var(--sidebar-width);height:calc(100vh - 60px);background:var(--card-dark);overflow-y:auto;transition:transform .3s;z-index:50}body.light .sidebar{background:var(--card-light);box-shadow:2px 0 10px #0000001a}.sidebar ul{list-style:none;padding:1rem 0}.sidebar li button{width:100%;padding:1rem 1.5rem;background:transparent;border:none;color:inherit;text-align:left;cursor:pointer;display:flex;align-items:center;gap:.75rem;font-size:1rem;transition:background .2s}.sidebar li button:hover{background:#4a90d933}.sidebar li button.active{background:var(--accent);color:#fff}.sidebar .icon{font-size:1.2rem}.sidebar a{text-decoration:none;color:var(--text-dark);display:block}body.light .sidebar a{color:var(--text-light)}.main-content{margin-left:var(--sidebar-width);margin-top:60px;padding:2rem;min-height:calc(100vh - 60px)}.section{max-width:800px;margin:0 auto}.section h2{font-size:2rem;margin-bottom:1.5rem;border-bottom:3px solid var(--accent);padding-bottom:.5rem}.concept-card,.highlight-box,.quiz-card{background:var(--card-dark);padding:1.5rem;border-radius:12px;margin-bottom:1.5rem;box-shadow:0 4px 15px #0003}body.light .concept-card,body.light .highlight-box,body.light .quiz-card{background:var(--card-light);box-shadow:0 4px 15px #0000001a}.concept-card h3,.highlight-box h3{color:var(--accent);margin-bottom:.75rem}.quiz-options{display:flex;gap:1rem;margin-top:1rem}.quiz-options button{padding:.75rem 1.5rem;background:var(--accent);color:#fff;border:none;border-radius:8px;cursor:pointer;transition:background .2s}.quiz-options button:hover{background:var(--accent-hover)}.correct{color:#4caf50;font-weight:700;margin-top:1rem}.incorrect{color:#f44336;font-weight:700;margin-top:1rem}.quiz-list{display:flex;flex-direction:column;gap:1.5rem}.quiz-option{display:flex;align-items:center;padding:1rem;background:#ffffff0d;border-radius:8px;cursor:pointer;transition:background .2s}body.light .quiz-option{background:#f0f0f0}.quiz-option:hover{background:#ffffff1a}body.light .quiz-option:hover{background:#e0e0e0}.quiz-option input{margin-right:1rem}.submit-quiz{margin-top:2rem;padding:1rem 2rem;background:var(--accent);color:#fff;border:none;font-size:1.1rem;border-radius:8px;cursor:pointer;width:100%}.submit-quiz:disabled{opacity:.5;cursor:not-allowed}.quiz-result{margin-top:2rem;padding:2rem;background:var(--card-dark);border-radius:12px;text-align:center;border:2px solid var(--accent)}body.light .quiz-result{background:var(--card-light)}.quiz-result.perfect{border-color:#4caf50;color:#4caf50}.fab{position:fixed;bottom:2rem;right:2rem;width:60px;height:60px;border-radius:50%;background:linear-gradient(135deg,#667eea,#764ba2);border:none;font-size:1.8rem;cursor:pointer;box-shadow:0 4px 20px #667eea66;transition:transform .3s,box-shadow .3s;z-index:1000}.fab:hover{transform:scale(1.1);box-shadow:0 6px 30px #667eea99}.ai-chat-window{position:fixed;bottom:6rem;right:2rem;width:380px;height:500px;background:#1a1a2efa;border-radius:16px;box-shadow:0 10px 40px #00000080;display:flex;flex-direction:column;opacity:0;visibility:hidden;transform:translateY(20px);transition:all .3s ease;z-index:1001;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);border:1px solid rgba(255,255,255,.1)}.ai-chat-window.open{opacity:1;visibility:visible;transform:translateY(0)}.ai-chat-header{display:flex;justify-content:space-between;align-items:center;padding:1rem 1.2rem;background:linear-gradient(135deg,#667eea,#764ba2);border-radius:16px 16px 0 0;color:#fff;font-weight:600}.ai-chat-close{background:none;border:none;color:#fff;font-size:1.2rem;cursor:pointer;opacity:.8;transition:opacity .2s}.ai-chat-close:hover{opacity:1}.ai-chat-messages{flex:1;overflow-y:auto;padding:1rem;display:flex;flex-direction:column;gap:.8rem}.ai-message{padding:.8rem 1rem;border-radius:12px;max-width:85%;line-height:1.5;font-size:.95rem}.ai-message.user{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff;align-self:flex-end;border-bottom-right-radius:4px}.ai-message.bot{background:#ffffff1a;color:#e0e0e0;align-self:flex-start;border-bottom-left-radius:4px}.ai-message.loading{opacity:.7;animation:pulse 1.5s infinite}@keyframes pulse{0%,to{opacity:.7}50%{opacity:.4}}.ai-chat-input-area{display:flex;gap:.5rem;padding:1rem;border-top:1px solid rgba(255,255,255,.1)}.ai-chat-input-area input{flex:1;padding:.8rem 1rem;border:1px solid rgba(255,255,255,.2);border-radius:8px;background:#ffffff0d;color:#fff;font-size:.95rem}.ai-chat-input-area input::placeholder{color:#ffffff80}.ai-chat-input-area input:focus{outline:none;border-color:#667eea}.ai-chat-input-area button{padding:.8rem 1.2rem;background:linear-gradient(135deg,#667eea,#764ba2);border:none;border-radius:8px;color:#fff;font-weight:600;cursor:pointer;transition:transform .2s}.ai-chat-input-area button:hover{transform:scale(1.05)}.ai-assistant .chat-container{background:var(--card-dark);border-radius:12px;overflow:hidden}body.light .ai-assistant .chat-container{background:var(--card-light)}.chat-messages{height:400px;overflow-y:auto;padding:1rem}.chat-messages .placeholder{color:#888;text-align:center;margin-top:150px}.message{padding:.75rem 1rem;margin-bottom:.75rem;border-radius:12px;max-width:80%}.message.user{background:var(--accent);color:#fff;margin-left:auto}.message.assistant{background:#ffffff1a}body.light .message.assistant{background:#e8e8e8}.chat-input{display:flex;padding:1rem;gap:.5rem;border-top:1px solid rgba(255,255,255,.1)}.chat-input input{flex:1;padding:.75rem;border:none;border-radius:8px;background:#ffffff1a;color:inherit}body.light .chat-input input{background:#f0f0f0}.chat-input button{padding:.75rem 1.5rem;background:var(--accent);color:#fff;border:none;border-radius:8px;cursor:pointer}.visual-placeholder{text-align:center;padding:2rem}.visualization{width:100%;min-height:400px;background:#ffffff0d;border-radius:10px;display:flex;align-items:center;justify-content:center;margin-bottom:2rem;overflow:hidden}body.light .visualization{background:#eaeaea}.viz-container p{margin-bottom:1rem;color:#888}@media(max-width:768px){.sidebar{transform:translate(-100%)}.sidebar.open{transform:translate(0)}.main-content{margin-left:0}}@media(max-width:480px){.ai-chat-window{width:calc(100% - 2rem);right:1rem;bottom:5rem;height:60vh}.fab{width:50px;height:50px;font-size:1.5rem;bottom:1rem;right:1rem}}