:root {
  --black: #0a0a0a;
  --ink: #161616;
  --white: #ffffff;
  --gray-50: #f6f6f6;
  --gray-200: #e4e4e4;
  --gray-500: #8a8a8a;
  --orange: #ff6a00;
  --orange-dark: #e05a00;
  --radius: 14px;
  --font: "Noto Sans JP", system-ui, sans-serif;
  --font-en: "Space Grotesk", "Noto Sans JP", sans-serif;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; background: var(--white); color: var(--ink);
  font-family: var(--font); line-height: 1.7; -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: inherit; }
[hidden] { display: none !important; }

/* header */
.site-header {
  position: sticky; top: 0; z-index: 10;
  display: flex; justify-content: space-between; align-items: center;
  padding: 14px 24px; background: rgba(10,10,10,.92); backdrop-filter: blur(8px);
  color: var(--white);
}
.logo { font-family: var(--font-en); font-weight: 700; font-size: 20px; letter-spacing: .12em; text-decoration: none; }
.logo span { color: var(--orange); }
.header-meta { font-family: var(--font-en); font-size: 12px; letter-spacing: .2em; text-transform: uppercase; color: var(--gray-500); }
.header-link { font-size: 14px; text-decoration: none; padding: 6px 14px; border: 1px solid #444; border-radius: 999px; transition: .2s; }
.header-link:hover { border-color: var(--orange); color: var(--orange); }

/* hero */
.hero { background: var(--black); color: var(--white); padding: 88px 24px 96px; position: relative; overflow: hidden; }
.hero::after {
  content: ""; position: absolute; right: -120px; bottom: -160px; width: 420px; height: 420px;
  border-radius: 50%; background: var(--orange);
}
.hero-inner { max-width: 1080px; margin: 0 auto; position: relative; z-index: 1; }
.eyebrow { font-family: var(--font-en); font-weight: 700; letter-spacing: .24em; font-size: 13px; color: var(--orange); margin: 0 0 14px; }
.hero h1 { font-size: clamp(34px, 7vw, 64px); line-height: 1.2; font-weight: 900; margin: 0 0 22px; letter-spacing: .02em; }
.hero h1 em { font-style: normal; color: var(--orange); }
.lead { max-width: 520px; color: #c9c9c9; margin: 0 0 32px; }
.progress { display: inline-flex; align-items: baseline; gap: 14px; padding: 10px 20px; border: 1px solid #3a3a3a; border-radius: 999px; background: var(--black); }
.progress-label { font-family: var(--font-en); font-size: 12px; letter-spacing: .2em; color: var(--gray-500); }
.progress-num { font-family: var(--font-en); font-weight: 700; font-size: 20px; color: var(--orange); }

/* layout */
.container { max-width: 1080px; margin: 0 auto; padding: 56px 24px 72px; }
.container.narrow { max-width: 860px; padding-top: 40px; }
.section-title { display: flex; align-items: baseline; gap: 14px; font-size: 22px; font-weight: 900; margin: 0 0 28px; }
.section-title span { font-family: var(--font-en); font-size: 13px; letter-spacing: .2em; color: var(--orange); }

/* grid */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }
.card {
  display: block; text-decoration: none; background: var(--white);
  border: 1px solid var(--gray-200); border-radius: var(--radius); overflow: hidden;
  transition: transform .25s, box-shadow .25s, border-color .25s;
}
.card:hover { transform: translateY(-6px); border-color: var(--orange); box-shadow: 0 16px 32px rgba(0,0,0,.12); }
.card-thumb { aspect-ratio: 16 / 9; background: var(--gray-50); overflow: hidden; }
.card-thumb img { width: 100%; height: 100%; object-fit: cover; transition: transform .4s; }
.card:hover .card-thumb img { transform: scale(1.04); }
.card-body { display: flex; justify-content: space-between; align-items: center; padding: 14px 18px; }
.card-no { font-family: var(--font-en); font-weight: 700; font-size: 18px; letter-spacing: .06em; }
.badge { font-size: 12px; font-weight: 700; padding: 3px 12px; border-radius: 999px; background: var(--gray-50); color: var(--gray-500); }
.badge.is-solved { background: var(--orange); color: var(--white); }

/* puzzle page */
.frame { margin: 0; border-radius: var(--radius); overflow: hidden; border: 2px solid var(--black); background: var(--white); box-shadow: 8px 8px 0 var(--black); }
.frame-accent { border-color: var(--orange); box-shadow: 8px 8px 0 var(--orange); }
.frame img { width: 100%; height: auto; }
.open-link { text-align: right; margin: 16px 0 0; font-size: 13px; }
.open-link a { color: var(--gray-500); text-decoration: none; }
.open-link a:hover { color: var(--orange); }

.answer-form { margin: 40px 0 8px; padding: 28px; background: var(--black); color: var(--white); border-radius: var(--radius); border: 2px solid var(--black); }
.answer-form label { display: block; font-family: var(--font-en); font-weight: 700; letter-spacing: .2em; font-size: 13px; color: var(--orange); margin-bottom: 12px; }
.answer-form label small { font-family: var(--font); letter-spacing: 0; color: var(--gray-500); margin-left: 10px; font-weight: 400; }
.row { display: flex; gap: 12px; }
.row input {
  flex: 1; min-width: 0; font: inherit; font-size: 18px; padding: 14px 18px; color: var(--white);
  background: #1c1c1c; border: 2px solid #333; border-radius: 10px; outline: none; transition: border-color .2s;
}
.row input:focus { border-color: var(--orange); }
.row input::placeholder { color: #666; }
.btn {
  font: inherit; font-weight: 700; padding: 14px 28px; border: 0; border-radius: 10px; cursor: pointer;
  background: var(--orange); color: var(--white); transition: background .2s, transform .1s; white-space: nowrap;
  text-decoration: none; display: inline-block;
}
.btn:hover { background: var(--orange-dark); }
.btn:active { transform: scale(.97); }
.btn-ghost { background: var(--black); }
.msg { min-height: 1.7em; margin: 12px 0 0; font-weight: 700; }
.msg.ok { color: var(--orange); }
.msg.ng { color: #ff8a8a; }
.answer-form.shake { animation: shake .4s; }
@keyframes shake { 20%, 60% { transform: translateX(-8px); } 40%, 80% { transform: translateX(8px); } }
.answer-form.is-correct { border-color: var(--orange); }

.result { margin-top: 56px; }
.result.pop { animation: pop .6s cubic-bezier(.2, .9, .3, 1.2); }
@keyframes pop { from { opacity: 0; transform: translateY(24px) scale(.97); } to { opacity: 1; transform: none; } }

.pager { display: flex; justify-content: space-between; align-items: center; margin-top: 64px; padding-top: 24px; border-top: 1px solid var(--gray-200); font-family: var(--font-en); font-weight: 700; }
.pager a { text-decoration: none; padding: 8px 4px; transition: color .2s; }
.pager a:hover { color: var(--orange); }
.notfound { font-size: 18px; margin-bottom: 24px; }

.site-footer { background: var(--black); color: var(--gray-500); text-align: center; padding: 28px; font-family: var(--font-en); font-size: 12px; letter-spacing: .2em; }

@media (max-width: 560px) {
  .site-header { padding: 12px 16px; }
  .hero { padding: 56px 16px 72px; }
  .container, .container.narrow { padding-left: 16px; padding-right: 16px; }
  .row { flex-direction: column; }
  .answer-form { padding: 20px; }
  .frame { box-shadow: 5px 5px 0 var(--black); }
  .frame-accent { box-shadow: 5px 5px 0 var(--orange); }
}
@media (prefers-reduced-motion: reduce) { * { animation: none !important; transition: none !important; } }