/* QUIZDON 共通スタイル — 白×赤のミニマル。画面の主役はコンテンツ */
:root{
  --bg:#FFFFFF; --panel:#F7F7F5; --ink:#17181A; --sub:#6E7076;
  --red:#D7361F; --red-deep:#B22A16; --line:#E9E9EB; --soft:#FBEAE6;
}
*{box-sizing:border-box;margin:0;padding:0}
[hidden]{display:none !important}
html{scroll-behavior:smooth}
body{
  background:var(--bg); color:var(--ink);
  font-family:"Hiragino Kaku Gothic ProN","Yu Gothic","Meiryo",sans-serif;
  font-size:16px; line-height:1.9; -webkit-font-smoothing:antialiased;
}
.mono{font-family:"SF Mono","Menlo","Consolas",monospace;font-variant-numeric:tabular-nums}
.wrap{max-width:820px;margin:0 auto;padding:0 20px}
a{color:var(--ink)}
a:focus-visible,button:focus-visible{outline:2px solid var(--red);outline-offset:3px}
h1,h2,h3{line-height:1.5;text-wrap:balance;font-weight:800}
h1{font-size:clamp(26px,5vw,38px)}
h2{font-size:clamp(20px,3vw,25px);margin-bottom:12px}
h3{font-size:17px;margin-bottom:6px}
section{padding:44px 0;border-top:1px solid var(--line)}
.eyebrow{display:block;font-size:12px;letter-spacing:.18em;color:var(--red);font-weight:700;margin-bottom:10px}
.lead{color:var(--sub);max-width:40em}
.note{font-size:13px;color:var(--sub)}

header.site{padding:14px 0}
.hrow{display:flex;justify-content:space-between;align-items:center;gap:12px}
.logo{font-weight:800;font-size:18px;letter-spacing:.05em;text-decoration:none}
.logo b{color:var(--red)}
.logo small{color:var(--sub);font-weight:400;font-size:11px;margin-left:6px}
nav.site a{font-size:13.5px;color:var(--sub);text-decoration:none;margin-left:14px}
nav.site a:hover{color:var(--ink)}

.btn{display:inline-block;cursor:pointer;text-decoration:none;text-align:center;border:none;
  font-family:inherit;font-weight:700;line-height:1.4;border-radius:10px;font-size:16px;padding:14px 28px}
.btn-main{background:var(--red);color:#fff}
.btn-main:hover{background:var(--red-deep)}
.btn-dark{background:var(--ink);color:var(--bg)}
.btn-line{background:transparent;color:var(--ink);border:1.5px solid var(--ink)}
.btn:disabled{opacity:.45;cursor:default}

.grid{display:grid;gap:14px}
.g2{grid-template-columns:1fr 1fr}
.g3{grid-template-columns:repeat(3,1fr)}
.card{border:1px solid var(--line);border-radius:12px;padding:20px;background:var(--bg)}
.card h3{margin-bottom:6px}
.card p{font-size:14px;color:var(--sub)}

details{border:1px solid var(--line);border-radius:10px;margin-bottom:10px;background:var(--bg)}
summary{cursor:pointer;font-weight:700;font-size:15.5px;padding:14px 18px;list-style-position:inside}
details .a{padding:0 18px 14px;color:var(--sub);font-size:14.5px}

footer.site{border-top:1px solid var(--line);padding:26px 0 42px;font-size:12.5px;color:var(--sub)}
footer.site a{color:var(--sub);margin-right:14px}

@media (max-width:640px){
  .g2,.g3{grid-template-columns:1fr}
  section{padding:34px 0}
}