body{font-family:Inter,sans-serif;background-color:#f3f4f6;display:flex;justify-content:center;align-items:center;min-height:100vh;margin:0}.app-card{background-color:#fff;padding:2.5rem;border-radius:1.5rem;box-shadow:0 10px 15px -3px #0000001a,0 4px 6px -2px #0000000d;max-width:450px;width:90%;transition:all .3s;position:relative;display:flex;flex-direction:column}.header-bg{background:linear-gradient(135deg,#4f46e5,#818cf8);color:#fff;padding:1rem 0;border-radius:1rem 1rem 0 0;margin:-2.5rem -2.5rem 1.5rem;text-align:center}.button{transition:all .2s;box-shadow:0 4px 6px #0000001a}.button:hover{transform:translateY(-1px);box-shadow:0 6px 10px #00000026}.teacher-mode{max-width:1400px!important;width:98%!important}::-webkit-scrollbar{width:8px;height:8px}::-webkit-scrollbar-track{background:#f1f1f1}::-webkit-scrollbar-thumb{background:#888;border-radius:4px}::-webkit-scrollbar-thumb:hover{background:#555}.loader{border:4px solid #f3f3f3;border-top:4px solid #3498db;border-radius:50%;width:30px;height:30px;animation:spin 1s linear infinite;margin:0 auto}@keyframes spin{0%{transform:rotate(0)}to{transform:rotate(360deg)}}.paste-area{border:2px dashed #cbd5e0;border-radius:.5rem;padding:1rem;background-color:#f9fafb;cursor:text;min-height:120px}.paste-area:focus{outline:none;border-color:#4f46e5}.stat-tab-btn{padding:8px 16px;border-bottom:2px solid transparent;color:#6b7280;font-weight:600;cursor:pointer}.stat-tab-btn.active{border-color:#4f46e5;color:#4f46e5}