*{box-sizing:border-box;padding:0;margin:0}html{min-height:100%}body,html{background:#fafafa}body,html{max-width:100vw;overflow-x:hidden;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen,Ubuntu,Cantarell,Fira Sans,Droid Sans,Helvetica Neue,sans-serif}body{color:rgb(var(--foreground-rgb));background:#fafafa;min-height:100vh}:root{--foreground-rgb:0,0,0;--background-start-rgb:214,219,220;--background-end-rgb:255,255,255;--primary-color:#6366f1;--secondary-color:#8b5cf6;--success-color:#10b981;--error-color:#ef4444;--warning-color:#f59e0b}a{color:inherit;text-decoration:none}button{cursor:pointer;padding:.5rem 1rem;border:none;border-radius:.375rem;font-size:1rem;transition:all .2s}button:hover{opacity:.9;transform:translateY(-1px)}button:active{transform:translateY(0)}.btn-primary{background-color:var(--primary-color);color:#fff}.btn-secondary{background-color:var(--secondary-color);color:#fff}.btn-success{background-color:var(--success-color);color:#fff}.btn-danger{background-color:var(--error-color);color:#fff}.container{max-width:1200px;margin:0 auto;padding:2rem}.card{background:#fff;border-radius:.5rem;padding:1.5rem;box-shadow:0 1px 3px 0 rgba(0,0,0,.1),0 1px 2px 0 rgba(0,0,0,.06)}.card,.input{margin-bottom:1rem}.input{width:100%;padding:.75rem;border:1px solid #d1d5db;border-radius:.375rem;font-size:1rem}.input:focus{outline:none;border-color:var(--primary-color);box-shadow:0 0 0 3px rgba(99,102,241,.1)}.grammar-box{background:linear-gradient(135deg,#8b5cf6,#6366f1);color:#fff;padding:1.5rem;border-radius:.5rem;margin-bottom:1rem;position:relative;cursor:pointer;transition:transform .2s}.grammar-box:hover{transform:translateY(-2px);box-shadow:0 4px 6px -1px rgba(0,0,0,.1)}.grammar-box:hover .history-arrow{opacity:1}.history-arrow{position:absolute;top:1rem;right:1rem;opacity:0;transition:opacity .2s;font-size:1.5rem}.feedback{padding:1rem;border-radius:.375rem;margin-top:1rem}.feedback.correct{background-color:#d1fae5;color:#065f46;border:1px solid #10b981}.feedback.incorrect{background-color:#fee2e2;color:#991b1b;border:1px solid #ef4444}.loading{display:inline-block;width:20px;height:20px;border-radius:50%;border:3px solid hsla(0,0%,100%,.3);border-top-color:#fff;animation:spin 1s ease-in-out infinite}@keyframes spin{to{transform:rotate(1turn)}}