*{margin:0;padding:0;box-sizing:border-box}body{font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen,Ubuntu,Cantarell,sans-serif;background-color:#f0f2f5;color:#333;line-height:1.6}.container{max-width:800px;margin:2rem auto;padding:0 1rem}.navbar{background-color:#fff;box-shadow:0 2px 4px #0000001a;padding:1rem 0}.navbar .container{display:flex;gap:2rem;margin:0 auto}.nav-link{text-decoration:none;color:#666;font-weight:500;padding:.5rem 1rem;border-radius:4px;transition:all .2s}.nav-link:hover{color:#06c;background-color:#f0f2f5}.nav-link.active{color:#06c;background-color:#e6f0ff}.card{background:#fff;border-radius:8px;box-shadow:0 2px 4px #0000001a;padding:1.5rem;margin-bottom:1rem;cursor:pointer;transition:transform .2s}.card:hover{transform:translateY(-2px)}.btn{padding:.5rem 1rem;border:none;border-radius:4px;cursor:pointer;font-weight:500;transition:background-color .2s}.btn-primary{background-color:#06c;color:#fff}.btn-primary:hover{background-color:#0052a3}.form-group{margin-bottom:1rem}.form-control{width:100%;padding:.5rem;border:1px solid #ddd;border-radius:4px;font-size:1rem}.flashcard{min-height:200px;display:flex;align-items:top;justify-content:center;text-align:center;font-size:1.25rem;perspective:1000px}.flashcard-inner{position:relative;width:100%;height:100%;text-align:center;transition:transform .6s;transform-style:preserve-3d}.flipped .flashcard-inner{transform:rotateY(180deg)}.flashcard-front,.flashcard-back{position:absolute;width:100%;height:100%;backface-visibility:hidden;padding:2rem}.flashcard-back{transform:rotateY(180deg);background-color:#f8f9fa}