body{background:#f7f9fc;color:#1d2939}.hero{background:linear-gradient(135deg,#eef4ff,#fff);border:1px solid #dbe7ff}.topic-card{scroll-margin-top:85px}.topic-card h2{font-size:1.35rem}.science-box{background:#eef8f1;border-left:4px solid #198754}.sticky-unit{top:80px}.answer{display:none}.answer.show{display:block}@media(max-width:767px){.display-4{font-size:2.1rem}.topic-card{border-radius:1rem}.unit-actions .btn{width:100%}}