:root{--ink:#203044;--muted:#536579;--blue:#174a70;--teal:#267b78;--line:#d9e2e9;--panel:#f4f8fa;--white:#fff}
*{box-sizing:border-box}
body{margin:0;background:#fff;color:var(--ink);font:16px/1.65 Arial,Helvetica,sans-serif}
header{background:var(--blue);color:#fff;padding:1.3rem max(1rem,calc((100% - 980px)/2))}
header p{margin:.25rem 0 0;color:#e4edf3}
nav{background:#edf3f6;border-bottom:1px solid var(--line);padding:.7rem max(1rem,calc((100% - 980px)/2));display:flex;gap:.5rem 1rem;flex-wrap:wrap}
nav a{color:var(--blue);font-weight:700;text-decoration:none}
nav a:hover, a:focus{text-decoration:underline}
main{max-width:980px;margin:0 auto;padding:1.5rem 1rem 3rem}
h1,h2,h3{line-height:1.25;color:var(--blue)}
h1{margin:.1rem 0 .5rem;font-size:2rem}h2{margin-top:2rem;border-bottom:1px solid var(--line);padding-bottom:.4rem}h3{margin-bottom:.35rem}
.lead{font-size:1.1rem;color:var(--muted);max-width:72ch}
.cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:1rem;margin:1.3rem 0}
.card,.panel{border:1px solid var(--line);border-radius:10px;padding:1rem;background:var(--white)}
.card{border-top:4px solid var(--teal)}
.card p{margin:.45rem 0}
.button,button{display:inline-block;background:var(--blue);color:#fff;border:0;border-radius:6px;padding:.65rem .9rem;font:inherit;font-weight:700;text-decoration:none;cursor:pointer}
.button:hover,button:hover{background:#103650}
.secondary{background:#e8f1f4;color:var(--blue)}
table{width:100%;border-collapse:collapse;margin:1rem 0}
th,td{padding:.65rem;text-align:left;border:1px solid var(--line);vertical-align:top}
th{background:#edf3f6}
.example{background:var(--panel);border-left:4px solid var(--teal);padding:.7rem 1rem;margin:.75rem 0}
.note{font-size:.95rem;color:var(--muted)}
.quiz-question{padding:1rem 0;border-bottom:1px solid var(--line)}
.quiz-question label{display:block;font-weight:700;margin-bottom:.4rem}
.quiz-question select,.quiz-question input{font:inherit;padding:.45rem;max-width:100%;border:1px solid #9aabb8;border-radius:5px;background:#fff}
.feedback{margin-top:.35rem;font-weight:700}
.correct{color:#17653d}.incorrect{color:#9a3b24}
.answer-list{columns:2;max-width:620px}
footer{border-top:1px solid var(--line);padding:1rem;color:var(--muted);text-align:center}
@media(max-width:600px){h1{font-size:1.65rem}table{font-size:.94rem}.answer-list{columns:1}}