:root{--primary: #4F46E5;--primary-hover: #4338CA;--primary-light: #EEF2FF;--secondary: #0D9488;--secondary-hover: #0F766E;--dark: #0F172A;--text-main: #334155;--text-muted: #64748B;--bg-main: #F8FAFC;--surface: #FFFFFF;--border: #E2E8F0;--radius-sm: 8px;--radius-md: 12px;--radius-lg: 16px;--shadow-sm: 0 1px 3px rgba(15, 23, 42, .08);--shadow-md: 0 4px 6px -1px rgba(15, 23, 42, .08), 0 2px 4px -2px rgba(15, 23, 42, .04);--shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, .08), 0 4px 6px -4px rgba(15, 23, 42, .04)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:Inter,-apple-system,sans-serif;line-height:1.6;color:var(--text-main);background-color:var(--bg-main);-webkit-font-smoothing:antialiased}.container{max-width:1200px;margin:0 auto;padding:0 24px}.navbar{background:var(--surface);padding:1rem 0;border-bottom:1px solid var(--border);position:sticky;top:0;z-index:100}.nav-container{display:flex;justify-content:space-between;align-items:center}.logo{font-size:1.5rem;font-weight:700;color:var(--dark);text-decoration:none;display:flex;align-items:center;gap:.5rem;letter-spacing:-.5px}.logo span,.logo-icon{color:var(--primary)}.nav-links{display:flex;list-style:none;gap:2rem;align-items:center}.nav-links a{color:var(--text-muted);text-decoration:none;font-weight:500;font-size:.95rem;transition:color .2s;display:flex;align-items:center;gap:.5rem}.nav-links a:hover{color:var(--primary)}.btn-nav{background:var(--primary-light);color:var(--primary)!important;padding:.5rem 1rem;border-radius:var(--radius-sm)}.btn-nav:hover{background:var(--primary);color:#fff!important}main{min-height:calc(100vh - 160px);padding:3rem 0}.hero{text-align:center;padding:5rem 0 4rem;max-width:800px;margin:0 auto}.hero-badge{display:inline-block;padding:.4rem 1rem;background:var(--primary-light);color:var(--primary);border-radius:20px;font-size:.85rem;font-weight:600;margin-bottom:1.5rem}.hero h1{font-size:3.5rem;line-height:1.1;margin-bottom:1.5rem;color:var(--dark);letter-spacing:-1px;font-weight:800}.text-gradient{background:linear-gradient(135deg,var(--primary),var(--secondary));-webkit-background-clip:text;-webkit-text-fill-color:transparent}.hero p{font-size:1.25rem;color:var(--text-muted);margin-bottom:2.5rem;padding:0 2rem}.hero-actions{display:flex;gap:1rem;justify-content:center}.features-header{text-align:center;margin:4rem 0 2rem}.features-header h2{color:var(--dark);font-size:2rem;letter-spacing:-.5px}.features{display:grid;grid-template-columns:repeat(auto-fit,minmax(320px,1fr));gap:2rem;margin-top:2rem}.feature-card{background:var(--surface);padding:2.5rem;border-radius:var(--radius-md);box-shadow:var(--shadow-sm);border:1px solid var(--border);transition:transform .3s,box-shadow .3s}.feature-card:hover{transform:translateY(-5px);box-shadow:var(--shadow-lg)}.feature-icon-wrapper{width:48px;height:48px;background:var(--primary-light);color:var(--primary);border-radius:var(--radius-sm);display:flex;align-items:center;justify-content:center;margin-bottom:1.5rem}.feature-card h2{font-size:1.25rem;margin-bottom:1rem;color:var(--dark)}.feature-list{list-style:none;margin-top:1rem}.feature-list li{padding:.5rem 0;display:flex;align-items:center;gap:.5rem;color:var(--text-muted)}.feature-list i{color:var(--secondary);width:18px;height:18px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;padding:.6rem 1.2rem;border:none;border-radius:var(--radius-sm);cursor:pointer;text-decoration:none;transition:all .2s;font-size:.95rem;font-weight:500}.btn-primary{background:var(--primary);color:#fff;box-shadow:0 2px 4px #4f46e54d}.btn-primary:hover{background:var(--primary-hover);transform:translateY(-1px);box-shadow:0 4px 6px #4f46e566}.btn-secondary{background:var(--surface);color:var(--text-main);border:1px solid var(--border)}.btn-secondary:hover{background:var(--bg-main);border-color:#cbd5e1}.btn-success{background:var(--secondary);color:#fff}.btn-success:hover{background:var(--secondary-hover)}.btn-large{padding:.875rem 1.75rem;font-size:1.05rem}.form-container,.grading-form{background:var(--surface);padding:2.5rem;border-radius:var(--radius-md);box-shadow:var(--shadow-md);max-width:800px;margin:0 auto;border:1px solid var(--border)}.form-group{margin-bottom:1.5rem}.form-group label{display:block;margin-bottom:.5rem;font-weight:500;color:var(--dark);font-size:.95rem}.form-group input,.form-group textarea,.form-group select{width:100%;padding:.875rem;border:1px solid var(--border);border-radius:var(--radius-sm);font-size:1rem;font-family:Inter,sans-serif;transition:border-color .2s,box-shadow .2s;background:#f8fafc}.form-group input:focus,.form-group textarea:focus,.form-group select:focus{outline:none;background:var(--surface);border-color:var(--primary);box-shadow:0 0 0 3px #4f46e526}.page-header{text-align:center;margin-bottom:3rem}.page-header h1{color:var(--dark);font-size:2.5rem;letter-spacing:-.5px;margin-bottom:.5rem}.page-header p{color:var(--text-muted);font-size:1.1rem}.results-container,.grading-summary{background:var(--surface);padding:2rem;border-radius:var(--radius-md);box-shadow:var(--shadow-md);margin-top:2rem;border:1px solid var(--border)}.topic-card{border:1px solid var(--border);padding:1.5rem;border-radius:var(--radius-sm);background:var(--surface);box-shadow:var(--shadow-sm)}.builder-sidebar{background:var(--surface);padding:1.5rem;border-radius:var(--radius-md);box-shadow:var(--shadow-sm);border:1px solid var(--border)}.builder-main{background:var(--surface);padding:2.5rem;border-radius:var(--radius-md);box-shadow:var(--shadow-sm);border:1px solid var(--border)}.subtopic-item{background:var(--bg-main);border:1px solid var(--border);transition:border-color .2s}.subtopic-item:hover{border-color:var(--primary)}.question-block{border:1px solid var(--border);background:var(--surface);box-shadow:var(--shadow-sm);border-radius:var(--radius-sm)}.score-card{border-radius:var(--radius-md);box-shadow:var(--shadow-sm)}.stat-item{border:1px solid var(--border);box-shadow:var(--shadow-sm)}footer{border-top:1px solid var(--border);color:var(--text-muted);text-align:center;padding:2rem 0;margin-top:4rem}.loading{background:#0f172acc;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px)}.spinner{border:4px solid rgba(255,255,255,.1);border-top:4px solid var(--primary)}.upload-zone{border:2px dashed var(--border);border-radius:var(--radius-md);padding:3rem 2rem;text-align:center;background:var(--bg-main);transition:all .3s ease;cursor:pointer;margin-bottom:1rem}.upload-zone:hover,.upload-zone.dragover{border-color:var(--primary);background:var(--primary-light)}.upload-zone i{width:48px;height:48px;color:var(--primary);margin-bottom:1rem}.upload-zone p{font-size:1.1rem;color:var(--dark);margin-bottom:.5rem}.upload-zone small{color:var(--text-muted);font-size:.85rem}.divider{display:flex;align-items:center;text-align:center;color:var(--text-muted);margin:2rem 0}.divider:before,.divider:after{content:"";flex:1;border-bottom:1px solid var(--border)}.divider span{padding:0 1rem;font-size:.9rem;font-weight:500}.modal-overlay{position:fixed;inset:0;background:#0f172ab3;display:flex;align-items:center;justify-content:center;z-index:1000;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px)}.modal-content{background:#fff;padding:2.5rem;border-radius:var(--radius-lg);max-width:450px;width:90%;text-align:center;box-shadow:var(--shadow-lg)}.success-icon{width:64px;height:64px;background:var(--success);border-radius:50%;display:flex;align-items:center;justify-content:center;margin:0 auto 1.5rem;box-shadow:0 0 0 10px #d1fae5}.modal-actions{margin-top:2rem;display:flex;flex-direction:column;gap:1rem}