@charset "utf-8";

:root {
  --navy: #0d1b2e;
  --navy-2: #16293f;
  --yellow: #f5c33c;
  --yellow-d: #d9a516;
  --bg: #ffffff;
  --bg-2: #f6f7f9;
  --bg-3: #eceef2;
  --fg: #1a2230;
  --fg-2: #5a6473;
  --fg-3: #8b95a3;
  --line: #e2e6ec;
  --ok: #1a8a5a;
  --ok-bg: #e8f6ef;
  --radius: 12px;
  --wrap: 780px;
  --font: "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Yu Gothic", "Noto Sans JP",
          system-ui, -apple-system, "Segoe UI", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101724;
    --bg-2: #16202f;
    --bg-3: #1e2a3b;
    --fg: #e8ecf2;
    --fg-2: #a3aebd;
    --fg-3: #7b8798;
    --line: #26334594;
    --ok: #4cc38a;
    --ok-bg: #14332a;
    --navy: #16293f;
    --navy-2: #1e3450;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--fg);
  line-height: 1.85;
  font-size: 16px;
  letter-spacing: .01em;
}
img { max-width: 100%; height: auto; }
a { color: inherit; }

.wrap { width: 100%; max-width: var(--wrap); margin-inline: auto; padding-inline: 20px; }

.skip {
  position: absolute; left: -9999px; top: 0; background: var(--yellow);
  color: var(--navy); padding: 10px 16px; z-index: 100; border-radius: 0 0 8px 0;
}
.skip:focus { left: 0; }

/* ---------- header ---------- */
.site-head {
  background: var(--navy);
  color: #fff;
  position: sticky; top: 0; z-index: 50;
  border-bottom: 1px solid #ffffff14;
}
.head-inner {
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; min-height: 60px; flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: #fff; }
.brand img { border-radius: 8px; display: block; }
.brand-text { display: flex; flex-direction: column; line-height: 1.25; }
.brand-text b { font-size: 17px; letter-spacing: .02em; }
.brand-text small { font-size: 11px; color: #ffffffa8; letter-spacing: .06em; }

.site-nav { display: flex; align-items: center; gap: 4px; flex-wrap: wrap; }
.site-nav a {
  text-decoration: none; color: #ffffffcc; font-size: 13.5px;
  padding: 7px 11px; border-radius: 999px; white-space: nowrap;
}
.site-nav a:hover { color: #fff; background: #ffffff1a; }
.site-nav .yt { background: var(--yellow); color: var(--navy); font-weight: 700; }
.site-nav .yt:hover { background: #ffd45e; color: var(--navy); }

/* ---------- main ---------- */
main { padding: 28px 0 64px; }

.crumbs { margin-bottom: 22px; font-size: 12.5px; color: var(--fg-3); }
.crumbs ol { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 6px; }
.crumbs li + li::before { content: "/"; margin-right: 6px; color: var(--fg-3); }
.crumbs a { color: var(--fg-3); text-decoration: none; }
.crumbs a:hover { color: var(--fg); text-decoration: underline; }
.crumbs li:last-child a { color: var(--fg-2); pointer-events: none; }

/* ---------- hero ---------- */
.hero { padding: 30px 0 42px; text-align: center; }
.hero-kicker {
  display: inline-block; margin: 0 0 14px; font-size: 12px; font-weight: 700;
  letter-spacing: .14em; color: var(--yellow-d); background: #f5c33c1f;
  padding: 5px 14px; border-radius: 999px;
}
.hero h1 { margin: 0 0 18px; font-size: clamp(27px, 6.4vw, 40px); line-height: 1.45; letter-spacing: .01em; }
.hero-lead { margin: 0 auto 26px; color: var(--fg-2); font-size: 15px; max-width: 34em; }
.hero-btns { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.hero-note { margin: 18px 0 0; font-size: 12.5px; color: var(--fg-3); }

.btn {
  display: inline-block; text-decoration: none; font-weight: 700; font-size: 15px;
  padding: 13px 26px; border-radius: 999px; background: var(--navy); color: #fff;
  border: 2px solid var(--navy); transition: transform .12s ease, box-shadow .12s ease;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 6px 18px #0d1b2e2e; }
.btn-ghost { background: transparent; color: var(--fg); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--fg-3); }
.btn-yt { background: var(--yellow); border-color: var(--yellow); color: var(--navy); }
.btn-yt:hover { background: #ffd45e; border-color: #ffd45e; }

/* ---------- series boxes ---------- */
.series-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 8px 0 46px; }
@media (max-width: 620px) { .series-grid { grid-template-columns: 1fr; } }
.sbox {
  display: block; text-decoration: none; padding: 22px 22px 20px;
  background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius);
  transition: border-color .15s ease, transform .12s ease;
}
.sbox:hover { border-color: var(--yellow); transform: translateY(-2px); }
.sbox h2 { margin: 12px 0 8px; font-size: 18px; }
.sbox p { margin: 0 0 14px; font-size: 13.5px; color: var(--fg-2); line-height: 1.75; }
.sbox .more { font-size: 13px; font-weight: 700; color: var(--yellow-d); }

.sec-title {
  font-size: 15px; letter-spacing: .08em; margin: 0 0 18px; padding-bottom: 10px;
  border-bottom: 2px solid var(--navy); display: inline-block;
}
.latest, .about-short { margin-bottom: 46px; }
.about-short p { font-size: 14.5px; color: var(--fg-2); margin: 0 0 12px; }
.about-short a { color: var(--yellow-d); font-weight: 700; text-decoration: none; }
.about-short a:hover { text-decoration: underline; }

/* ---------- page head ---------- */
.page-head { margin-bottom: 30px; }
.page-head h1 { margin: 0 0 12px; font-size: clamp(22px, 5vw, 29px); line-height: 1.5; }
.page-head .lead { margin: 0 0 10px; color: var(--fg-2); font-size: 14.5px; }
.page-head .count { margin: 0; font-size: 13px; color: var(--fg-3); }
.page-head .count b { color: var(--fg); font-size: 15px; }
.page-head.nf { text-align: center; padding: 40px 0; }

/* ---------- cards ---------- */
.cards { display: grid; gap: 12px; }
.card {
  display: block; text-decoration: none; padding: 18px 20px;
  background: var(--bg-2); border: 1px solid var(--line); border-radius: var(--radius);
  transition: border-color .15s ease, transform .12s ease;
}
.card:hover { border-color: var(--yellow); transform: translateY(-2px); }
.card-meta { display: flex; align-items: center; gap: 9px; flex-wrap: wrap; margin-bottom: 10px; }
.card-q { margin: 0 0 6px; font-size: 15.5px; font-weight: 600; line-height: 1.65; }
.card-jp { margin: 0; font-size: 13px; color: var(--fg-3); }

.tag {
  font-size: 11px; font-weight: 700; letter-spacing: .04em;
  padding: 3px 10px; border-radius: 999px; background: var(--navy); color: #fff;
}
.tag-part5 { background: var(--yellow-d); color: #fff; }
.lv { font-size: 11.5px; color: var(--fg-2); background: var(--bg-3); padding: 3px 9px; border-radius: 999px; }
.card-meta time { font-size: 11.5px; color: var(--fg-3); margin-left: auto; }

/* ---------- post ---------- */
.post-head { margin-bottom: 26px; }
.post-head h1 { margin: 10px 0 0; font-size: clamp(20px, 4.6vw, 26px); line-height: 1.5; }
.post-head .card-meta time { margin-left: 0; }

.box {
  background: var(--bg-2); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 24px 22px; margin-bottom: 20px;
}
.q-label {
  margin: 0 0 14px; font-size: 11.5px; letter-spacing: .12em; color: var(--fg-3);
  font-weight: 700;
}
.q-en {
  margin: 0 0 20px; font-size: 19px; font-weight: 600; line-height: 1.7;
  font-family: Georgia, "Times New Roman", serif; letter-spacing: 0;
}
.blank { color: var(--yellow-d); letter-spacing: -.06em; }

.choices { list-style: none; margin: 0; padding: 0; display: grid; gap: 9px; counter-reset: c; }
.choice {
  display: flex; align-items: flex-start; gap: 12px; padding: 13px 15px;
  background: var(--bg); border: 1px solid var(--line); border-radius: 9px;
  position: relative;
}
.choice.is-answer { border-color: var(--ok); background: var(--ok-bg); }
.c-l {
  flex: none; width: 25px; height: 25px; border-radius: 50%;
  background: var(--bg-3); color: var(--fg-2);
  display: flex; align-items: center; justify-content: center;
  font-size: 12.5px; font-weight: 700; margin-top: 2px;
}
.choice.is-answer .c-l { background: var(--ok); color: #fff; }
.c-body { display: flex; flex-direction: column; gap: 2px; flex: 1; min-width: 0; }
.c-en { font-size: 15px; line-height: 1.65; }
.c-jp { font-size: 12.5px; color: var(--fg-3); }
.c-note { font-size: 12.5px; color: var(--fg-2); margin-top: 3px; }
.c-badge {
  flex: none; align-self: center; font-size: 10.5px; font-weight: 700;
  color: var(--ok); border: 1px solid var(--ok); padding: 2px 8px; border-radius: 999px;
}

.reveal {
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--bg-2); margin-bottom: 20px; overflow: hidden;
}
.reveal summary {
  cursor: pointer; padding: 16px 22px; font-weight: 700; font-size: 14.5px;
  list-style: none; user-select: none; display: flex; align-items: center; gap: 9px;
}
.reveal summary::-webkit-details-marker { display: none; }
.reveal summary::before {
  content: "▶"; font-size: 10px; color: var(--yellow-d); transition: transform .2s ease;
}
.reveal[open] summary::before { transform: rotate(90deg); }
.reveal summary:hover { background: var(--bg-3); }
.reveal-body { padding: 4px 22px 24px; }

.answer-card {
  display: flex; align-items: flex-start; gap: 12px; padding: 14px 16px;
  background: var(--ok-bg); border: 1px solid var(--ok);
  border-radius: 9px; margin-bottom: 18px;
}
.answer-card .c-l { background: var(--ok); color: #fff; }
.lbl {
  display: inline-block; font-size: 11px; font-weight: 700; letter-spacing: .08em;
  color: var(--fg-3); background: var(--bg-3); padding: 2px 9px; border-radius: 4px;
  margin-right: 10px; vertical-align: 2px;
}
.q-jp, .full-sent { margin: 0 0 14px; font-size: 14.5px; line-height: 1.8; }
.full-sent { font-family: Georgia, serif; }

.choice-trans { margin: 0 0 16px; }
.choice-trans ul { list-style: none; margin: 10px 0 0; padding: 0; display: grid; gap: 6px; }
.choice-trans li { font-size: 13.5px; color: var(--fg-2); display: flex; gap: 10px; }
.t-l {
  flex: none; width: 20px; height: 20px; border-radius: 50%; background: var(--bg-3);
  color: var(--fg-2); display: flex; align-items: center; justify-content: center;
  font-size: 11px; font-weight: 700; margin-top: 4px;
}

.explains { margin: 0 0 16px; padding: 0; list-style: none; display: grid; gap: 10px; }
.explains li {
  font-size: 14.5px; line-height: 1.8; padding-left: 15px; position: relative; color: var(--fg-2);
}
.explains li::before {
  content: ""; position: absolute; left: 0; top: 12px;
  width: 5px; height: 5px; border-radius: 50%; background: var(--yellow-d);
}
.point {
  margin: 0; padding: 15px 17px; background: #f5c33c1f;
  border-left: 3px solid var(--yellow); border-radius: 0 8px 8px 0;
  font-size: 14.5px; font-weight: 600; line-height: 1.8;
}
.point .lbl { background: var(--yellow); color: var(--navy); }

.box-kw h2 { margin: 0 0 12px; font-size: 13px; letter-spacing: .08em; color: var(--fg-3); }
.kw-word { margin: 0 0 8px; font-size: 22px; font-weight: 700; font-family: Georgia, serif; }
.kw-mean {
  display: block; font-size: 14px; font-weight: 400; color: var(--fg-2);
  font-family: var(--font); margin-top: 2px;
}
.kw-ex { margin: 0; font-size: 14px; color: var(--fg-2); font-family: Georgia, serif; font-style: italic; }

.cta {
  background: var(--navy); color: #fff; border-radius: var(--radius);
  padding: 26px 24px; text-align: center; margin: 30px 0 26px;
}
.cta p { margin: 0 0 18px; font-size: 14px; line-height: 1.8; color: #ffffffcf; }
.cta b { color: #fff; font-size: 15.5px; }

.postnav { display: flex; gap: 10px; margin-bottom: 18px; }
.pn {
  flex: 1; text-decoration: none; padding: 13px 16px; border: 1px solid var(--line);
  border-radius: 9px; font-size: 14px; font-weight: 600; background: var(--bg-2);
  transition: border-color .15s ease;
}
.pn:hover { border-color: var(--yellow); }
.pn span { display: block; font-size: 11px; color: var(--fg-3); font-weight: 400; margin-bottom: 1px; }
.pn.next { text-align: right; }
.backlink { text-align: center; margin: 0; font-size: 13.5px; }
.backlink a { color: var(--fg-2); }

/* ---------- prose ---------- */
.prose h2 {
  margin: 34px 0 14px; font-size: 18px; padding-left: 12px;
  border-left: 4px solid var(--yellow); line-height: 1.5;
}
.prose p { margin: 0 0 15px; font-size: 15px; color: var(--fg-2); }
.prose ul { margin: 0 0 15px; padding-left: 1.3em; }
.prose li { font-size: 15px; color: var(--fg-2); margin-bottom: 9px; }
.prose a { color: var(--yellow-d); font-weight: 600; }
.prose b { color: var(--fg); }
.updated { font-size: 12.5px; color: var(--fg-3); margin-top: 30px; }

/* ---------- footer ---------- */
.site-foot { background: var(--bg-2); border-top: 1px solid var(--line); padding: 40px 0 30px; }
.foot-cta {
  background: var(--navy); color: #fff; border-radius: var(--radius);
  padding: 26px 24px; text-align: center; margin-bottom: 30px;
}
.foot-cta p { margin: 0 0 16px; font-size: 13.5px; color: #ffffffc4; line-height: 1.8; }
.foot-cta b { display: block; color: #fff; font-size: 15.5px; margin-bottom: 4px; }
.foot-nav {
  display: flex; flex-wrap: wrap; gap: 8px 20px; justify-content: center;
  padding-bottom: 20px; border-bottom: 1px solid var(--line);
}
.foot-nav a { font-size: 13px; color: var(--fg-2); text-decoration: none; }
.foot-nav a:hover { color: var(--fg); text-decoration: underline; }
.copy { text-align: center; font-size: 12px; color: var(--fg-3); margin: 18px 0 0; }

@media (max-width: 560px) {
  body { font-size: 15.5px; }
  .head-inner { min-height: 54px; padding-block: 8px; }
  .brand-text small { display: none; }
  .site-nav a { padding: 6px 9px; font-size: 12.5px; }
  .box { padding: 20px 16px; }
  .reveal summary { padding: 14px 16px; }
  .reveal-body { padding: 4px 16px 20px; }
  .q-en { font-size: 17px; }
  .postnav { flex-direction: column; }
  .pn.next { text-align: left; }
}