.quiz-button{background:#fff;color:#667eea;border:none;padding:15px 30px;font-size:1.1em;border-radius:25px;cursor:pointer;margin:10px;transition:all .3s ease;font-weight:600;box-shadow:0 4px 6px rgba(0,0,0,.1)}.quiz-button:hover{transform:scale(1.05);box-shadow:0 6px 12px rgba(0,0,0,.15)}.progress-item.checked .checkbox{background:#fff;color:#667eea}.flip-card.flipped{transform:rotateY(180deg)}@media (max-width:768px){.quiz-button{padding:12px 20px;font-size:1em}}