:root{--primary: #3b82f6;--primary-light: #eff6ff;--success: #10b981;--danger: #ef4444;--bg: #f8fafc;--card-bg: #ffffff;--text-main: #1e293b;--text-muted: #64748b;--radius: 16px;--shadow: 0 4px 6px -1px rgba(0, 0, 0, .1), 0 2px 4px -1px rgba(0, 0, 0, .06)}body{margin:0;font-family:Inter,system-ui,-apple-system,sans-serif;background-color:var(--bg);color:var(--text-main)}.app-container{max-width:1000px;margin:0 auto;min-height:100vh;display:flex;flex-direction:column}.app-header{padding:20px;background:#fff;border-bottom:1px solid #e2e8f0;display:flex;flex-direction:column;gap:15px}.logo-section{display:flex;align-items:center;gap:10px}.logo-icon{color:var(--primary);width:32px;height:32px}.logo-section h1{margin:0;font-size:1.5rem;font-weight:800;background:linear-gradient(135deg,#3b82f6,#2563eb);-webkit-background-clip:text;-webkit-text-fill-color:transparent}.cloud-badge{font-size:12px;color:var(--text-muted);background:var(--bg);padding:4px 10px;border-radius:20px;display:flex;align-items:center;gap:4px;margin-left:auto}.nav-tabs{display:flex;gap:10px}.nav-tabs button{padding:10px 16px;border:none;background:transparent;border-radius:10px;cursor:pointer;display:flex;align-items:center;gap:8px;font-weight:600;color:var(--text-muted);transition:all .2s}.nav-tabs button.active{background:var(--primary-light);color:var(--primary)}.content-area{padding:24px;flex:1}.card{background:#fff;border-radius:var(--radius);padding:20px;box-shadow:var(--shadow)}.add-panel{display:flex;flex-direction:column;gap:12px;margin-bottom:24px}.input-row{display:flex;gap:12px}.input-row input,.input-row select{padding:12px;border:1px solid #e2e8f0;border-radius:10px;font-size:14px;outline:none}.input-row input:focus{border-color:var(--primary)}.input-row input[placeholder]{flex:2}.input-group{display:flex;align-items:center;gap:8px;background:#f1f5f9;padding:0 12px;border-radius:10px;color:var(--text-muted)}.btn-primary{background:var(--primary);color:#fff;border:none;padding:0 24px;border-radius:10px;font-weight:600;cursor:pointer;display:flex;align-items:center;gap:8px}.filter-bar{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px}.chip{padding:6px 14px;border:1px solid #e2e8f0;background:#fff;border-radius:20px;font-size:13px;cursor:pointer;margin-left:8px}.chip.active{background:var(--text-main);color:#fff;border-color:var(--text-main)}.homework-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:20px}.hw-card{background:#fff;border-radius:var(--radius);padding:20px;border:1px solid #e2e8f0;transition:transform .2s,box-shadow .2s;position:relative}.hw-card:hover{transform:translateY(-4px);box-shadow:0 10px 15px -3px #0000001a}.hw-card.is-done{opacity:.7;background:#f8fafc}.hw-header{display:flex;justify-content:space-between;margin-bottom:12px}.subject-tag{font-size:11px;font-weight:700;padding:2px 8px;border-radius:4px;text-transform:uppercase}.subject-tag.数学{background:#fee2e2;color:#ef4444}.subject-tag.语文{background:#fef3c7;color:#d97706}.subject-tag.英语{background:#dcfce7;color:#16a34a}.hw-meta{display:flex;gap:15px;font-size:12px;color:var(--text-muted);margin:10px 0}.overdue{color:var(--danger);font-weight:600}.progress-container{margin:15px 0;display:flex;align-items:center;gap:10px}.progress-bar{flex:1;height:6px;background:#f1f5f9;border-radius:3px;overflow:hidden}.progress-fill{height:100%;background:var(--primary)}.btn-complete{width:100%;padding:10px;border-radius:8px;border:1px solid var(--primary);background:transparent;color:var(--primary);font-weight:600;cursor:pointer;display:flex;justify-content:center;align-items:center;gap:8px}.btn-complete.done{background:var(--success);border-color:var(--success);color:#fff}.help-view{max-width:600px;margin:0 auto}.ai-intro{display:flex;gap:15px;margin-bottom:20px}.ai-avatar{font-size:40px}.ai-input-area textarea{width:100%;height:120px;padding:15px;border:1px solid #e2e8f0;border-radius:12px;resize:none;margin-bottom:15px;font-family:inherit}.btn-ai{width:100%;padding:14px;background:linear-gradient(135deg,#6366f1,#3b82f6);color:#fff;border:none;border-radius:12px;font-weight:700;cursor:pointer}.ai-response{margin-top:24px;padding:20px;background:#f5f3ff;border-radius:12px;border-left:4px solid #8b5cf6}.response-header{font-weight:700;color:#6d28d9;margin-bottom:8px}.response-content{line-height:1.6;white-space:pre-wrap}.loading-screen{height:100vh;display:flex;align-items:center;justify-content:center;color:var(--text-muted)}