:root{
  --bg:#f4f7fb; --surface:#ffffff; --surface-2:#f0f5fb; --head:rgba(255,255,255,.88);
  --ink:#0f1c2e; --ink-2:#3a4a60; --muted:#6b7a90; --line:#e2e8f1;
  --brand:#0055a1; --brand-ink:#ffffff; --brand-soft:#e8f1fb;
  --ok:#11845f; --ok-soft:#e3f5ec; --warn:#a96b06; --warn-soft:#fdf3e1;
  --f-jp:"Zen Kaku Gothic New","Hiragino Sans","Yu Gothic UI","Meiryo",sans-serif;
  --f-en:"Outfit","Zen Kaku Gothic New","Helvetica Neue",Arial,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    --bg:#0d1520; --surface:#152030; --surface-2:#1b293b; --head:rgba(21,32,48,.9);
    --ink:#e8eef6; --ink-2:#b9c5d5; --muted:#8a99ae; --line:#26374b;
    --brand:#6bb2ff; --brand-ink:#08203b; --brand-soft:#17304d;
    --ok:#4fd3a2; --ok-soft:#123528; --warn:#f0b54a; --warn-soft:#3a2c10;
    color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --bg:#0d1520; --surface:#152030; --surface-2:#1b293b; --head:rgba(21,32,48,.9);
  --ink:#e8eef6; --ink-2:#b9c5d5; --muted:#8a99ae; --line:#26374b;
  --brand:#6bb2ff; --brand-ink:#08203b; --brand-soft:#17304d;
  --ok:#4fd3a2; --ok-soft:#123528; --warn:#f0b54a; --warn-soft:#3a2c10;
  color-scheme:dark;
}
*,*::before,*::after{box-sizing:border-box}
html{scroll-padding-top:72px}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--f-jp);font-size:15px;line-height:1.75;letter-spacing:.02em;-webkit-font-smoothing:antialiased}
a{color:inherit}
button{font:inherit;color:inherit;cursor:pointer;border:0;background:none;padding:0}
h1,h2,h3{margin:0;line-height:1.4;letter-spacing:.03em}
p{margin:0}
img{max-width:100%}
.num{font-family:var(--f-en);font-feature-settings:"tnum";letter-spacing:0}
:focus-visible{outline:3px solid var(--brand);outline-offset:2px;border-radius:6px}
.wrap{max-width:1120px;margin:0 auto;padding:0 20px}
.wrap.narrow{max-width:920px}

/* header */
.top{position:sticky;top:0;z-index:20;background:var(--head);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.top .wrap{display:flex;align-items:center;gap:16px;height:60px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-weight:700;min-width:0}
.brand-mark{width:32px;height:32px;border-radius:9px;background:var(--brand);color:var(--brand-ink);display:grid;place-items:center;font-family:var(--f-en);font-weight:600;font-size:15px;flex:none}
.brand small{display:block;font-size:11px;color:var(--muted);font-weight:500;line-height:1.2}
.brand b{display:block;font-size:15px;line-height:1.3;white-space:nowrap}
.top nav{margin-left:auto;display:flex;gap:4px}
.top nav a{text-decoration:none;font-size:14px;font-weight:500;color:var(--ink-2);padding:6px 12px;border-radius:8px;white-space:nowrap}
.top nav a:hover{background:var(--surface-2)}
.top nav a[aria-current="page"]{color:var(--brand);background:var(--brand-soft)}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:42px;padding:0 18px;border-radius:999px;font-weight:700;font-size:14px;text-decoration:none;white-space:nowrap;transition:background .15s,border-color .15s,color .15s}
.btn-primary{background:var(--brand);color:var(--brand-ink)}
.btn-primary:hover{filter:brightness(1.08)}
.btn-line{border:1px solid var(--line);background:var(--surface);color:var(--ink-2)}
.btn-line:hover{border-color:var(--brand);color:var(--brand)}
.btn-sm{min-height:36px;padding:0 14px;font-size:13px}
.btn svg{width:16px;height:16px;flex:none}
.btn:disabled{opacity:.5;cursor:not-allowed}

/* home */
.hero{padding:44px 0 28px;display:grid;grid-template-columns:minmax(0,1.3fr) minmax(0,1fr);gap:32px;align-items:end}
.hero .org{font-size:13px;color:var(--muted);font-weight:500}
.hero h1{font-size:clamp(28px,4.4vw,40px);margin:6px 0 12px;letter-spacing:.05em}
.hero p.lead{color:var(--ink-2);max-width:32em}
.status-panel{background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:20px}
.status-panel .count{display:flex;align-items:baseline;gap:8px;font-weight:700}
.status-panel .count .big{font-family:var(--f-en);font-size:40px;font-weight:600;line-height:1;color:var(--brand)}
.status-panel .count .of{font-family:var(--f-en);font-size:18px;color:var(--muted)}
.meter{height:6px;border-radius:3px;background:var(--surface-2);overflow:hidden;margin:12px 0 16px}
.meter i{display:block;height:100%;background:var(--ok);border-radius:3px}
.resume-link{display:flex;flex-direction:column;gap:2px;padding:12px 14px;border-radius:12px;background:var(--brand-soft);text-decoration:none}
.resume-link small{font-size:12px;color:var(--muted)}
.resume-link b{color:var(--brand);font-size:14px}

.home-note{display:flex;gap:10px;align-items:flex-start;margin:0 0 16px;font-size:13px;color:var(--ink-2);background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:12px 16px}
.home-note svg{width:18px;height:18px;flex:none;margin-top:2px;color:var(--brand)}
.home-note a{color:var(--brand);font-weight:700}

.subjects{display:grid;grid-template-columns:1fr 1fr;gap:14px;padding-bottom:40px}
.subject.pair{grid-column:1 / -1}
.subject.single .lec-pair{grid-template-columns:1fr}
@media (max-width:640px){ .subjects{grid-template-columns:1fr} }
.subject{display:flex;flex-direction:column;gap:14px;background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:18px;border-top:4px solid var(--sc)}
.subject-info{display:flex;flex-wrap:wrap;align-items:baseline;gap:4px 16px}
.subject-info h2{font-size:18px}
.subject-info .topics{font-size:13px;color:var(--muted)}
.lec-pair{display:grid;grid-template-columns:1fr 1fr;gap:16px}
.lec{display:flex;flex-direction:column;gap:10px;text-decoration:none;padding:8px 8px 12px;border-radius:14px;border:1px solid transparent}
.lec:hover{background:var(--surface-2);border-color:var(--line)}
.thumb{position:relative;aspect-ratio:16/9;border-radius:10px;overflow:hidden;background:var(--surface-2)}
.thumb img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover}
.thumb .dur{position:absolute;right:8px;bottom:10px;font-family:var(--f-en);font-size:12px;color:#fff;background:rgba(0,0,0,.65);padding:1px 7px;border-radius:5px}
.thumb .soon{position:absolute;right:8px;bottom:10px;font-size:12px;font-weight:700;color:#fff;background:rgba(0,0,0,.65);padding:1px 9px;border-radius:5px}
.thumb .done{position:absolute;right:8px;top:8px;width:28px;height:28px;box-shadow:0 2px 6px rgba(0,0,0,.25);border-radius:50%;background:#fff;color:#11845f;display:grid;place-items:center}
.thumb .done svg{width:17px;height:17px}
.thumb .pbar{position:absolute;left:0;right:0;bottom:0;height:5px;background:rgba(0,0,0,.3)}
.thumb .pbar i{display:block;height:100%;background:#e5322d}
.lec .lvl{font-size:12px;font-weight:700;color:var(--sc)}
.lec h3{font-size:16px;margin:1px 0 6px}
.badge{display:inline-flex;align-items:center;gap:4px;font-size:12px;font-weight:700;padding:1px 9px;border-radius:999px;background:var(--surface-2);color:var(--muted)}
.badge svg{width:12px;height:12px}
.badge.ok{background:var(--ok-soft);color:var(--ok)}
.badge.mid{background:var(--brand-soft);color:var(--brand)}
.badge.wait{background:var(--warn-soft);color:var(--warn)}
.kitline{display:flex;align-items:center;gap:4px;margin-top:5px;font-size:12px;color:var(--muted)}
.kitline svg{width:13px;height:13px;flex:none}
.kitline.open{color:var(--ok);font-weight:700}

/* lecture page */
.crumbs{display:flex;flex-wrap:wrap;gap:6px;font-size:13px;color:var(--muted);padding:18px 0 14px}
.crumbs a{text-decoration:none;color:var(--brand)}
.player{position:relative;background:#000;border-radius:16px;overflow:hidden;aspect-ratio:16/9}
.player video{display:block;width:100%;height:100%;background:#000}
.player > img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover}
.overlay{position:absolute;inset:0;display:none;align-items:center;justify-content:center;flex-direction:column;gap:14px;background:rgba(5,12,22,.66);color:#fff;text-align:center;padding:20px}
.overlay.on{display:flex}
.overlay p{font-size:15px}
.overlay .row{display:flex;flex-wrap:wrap;gap:10px;justify-content:center}
.overlay .btn-line{background:rgba(255,255,255,.1);color:#fff;border-color:rgba(255,255,255,.45)}
.overlay .btn-line:hover{color:#fff;border-color:#fff}
.overlay .btn-primary{background:#fff;color:#0b2a4d}
.player-bar{display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;margin-top:10px;font-size:13px;color:var(--muted)}
.speeds{display:inline-flex;gap:2px;background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:3px}
.speeds button{padding:3px 11px;border-radius:999px;font-size:12px;font-weight:700;color:var(--ink-2)}
.speeds button[aria-pressed="true"]{background:var(--brand);color:var(--brand-ink)}

.lec-head{display:flex;flex-wrap:wrap;align-items:flex-start;gap:12px 20px;margin:18px 0 6px}
.lec-head h1{font-size:22px;flex:1 1 280px}
.lec-head .meta{font-size:13px;color:var(--muted);margin-top:2px}
.lec-head .lvl{color:var(--sc);font-weight:700}

.panel{background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:18px}
.section{margin-top:22px}
.section h2{font-size:17px;margin-bottom:8px}
.summary{color:var(--ink-2)}
.points{margin:10px 0 0;padding-left:1.3em;color:var(--ink-2)}
.points li{margin:2px 0}

/* kit */
.kitcard{border-left:4px solid var(--sc)}
.kit-head{display:grid;grid-template-columns:auto minmax(0,1fr);gap:16px;align-items:start}
.kit-head .ico{width:44px;height:44px;border-radius:12px;background:color-mix(in srgb,var(--sc) 14%,transparent);color:var(--sc);display:grid;place-items:center}
.kit-head .ico svg{width:22px;height:22px}
.kit-head small{color:var(--muted);font-size:12px}
.kit-head b{display:block;font-size:16px}
.kit-head p{font-size:13px;color:var(--ink-2);margin-top:4px}
.files{list-style:none;margin:14px 0 0;padding:0;display:flex;flex-direction:column;gap:8px}
.file{display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;padding:10px 12px;border-radius:12px;background:var(--surface-2)}
.file .fname{flex:1 1 220px;min-width:0;display:flex;flex-direction:column}
.file .fname b{font-size:14px}
.file .fname small{font-size:12px;color:var(--muted)}
.file .acts{display:flex;gap:6px;flex-wrap:wrap}
.soon-box{display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;margin-top:14px;padding:12px 14px;border-radius:12px;background:var(--surface-2);font-size:13px;color:var(--muted)}
.soon-tag{display:inline-flex;align-items:center;font-family:var(--f-en);font-size:13px;font-weight:600;letter-spacing:.04em;padding:2px 12px;border-radius:999px;background:var(--warn-soft);color:var(--warn)}
.kitcard.empty{color:var(--muted);font-size:14px}
.kit-note{display:flex;gap:10px;margin-top:10px;font-size:13px;line-height:1.7;color:var(--ink-2);background:var(--surface-2);border-radius:12px;padding:12px 14px}
.kit-note svg{width:18px;height:18px;flex:none;margin-top:2px;color:var(--brand)}

.pager{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:26px 0 8px}
.pager a{display:flex;flex-direction:column;gap:2px;padding:12px 16px;border:1px solid var(--line);border-radius:12px;text-decoration:none;background:var(--surface)}
.pager a:hover{border-color:var(--brand)}
.pager a small{font-size:12px;color:var(--muted)}
.pager a b{font-size:14px}
.pager .next{text-align:right;grid-column:2}
.ask{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:12px;margin:18px 0 48px;padding:16px 18px;border-radius:14px;background:var(--surface-2)}
.ask p{font-size:14px;color:var(--ink-2)}

/* downloads page */
.page{padding:28px 0 60px}
.page > h1{font-size:26px;margin-bottom:8px}
.page > .lead{color:var(--ink-2);margin-bottom:22px}
.dl-list{display:flex;flex-direction:column;gap:14px}
.dl-list .kitcard .kit-head small a{color:var(--brand)}

/* contact */
.contact{max-width:640px}
.field{margin-bottom:16px}
.field label{display:block;font-size:13px;font-weight:700;color:var(--ink-2);margin-bottom:6px}
.field label small{font-weight:400;color:var(--muted);margin-left:6px}
.input{width:100%;min-height:46px;padding:10px 14px;border:1px solid var(--line);border-radius:10px;background:var(--surface);color:var(--ink);font:inherit}
.input:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px var(--brand-soft)}
textarea.input{min-height:140px;resize:vertical;line-height:1.7}
.err{color:#d24b4b;font-size:13px;min-height:20px}
.faq{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:16px 18px;margin-bottom:24px}
.faq h2{font-size:15px;margin-bottom:6px}
.faq p,.faq ul{font-size:14px;color:var(--ink-2)}
.faq ul{margin:6px 0 0;padding-left:1.2em}
.notice{padding:16px 18px;border-radius:14px;background:var(--warn-soft);color:var(--warn);font-size:14px}
.sent{padding:24px;border-radius:16px;background:var(--ok-soft);color:var(--ok)}
.sent b{display:block;font-size:17px;margin-bottom:4px}

footer{border-top:1px solid var(--line);padding:22px 0 40px;font-size:13px;color:var(--muted)}
footer .wrap{display:flex;flex-wrap:wrap;gap:12px 20px;align-items:center}
footer a{color:var(--ink-2)}
footer .reset{margin-left:auto;font-size:12px;text-decoration:underline;color:var(--muted)}

.toast{position:fixed;left:50%;bottom:24px;transform:translate(-50%,20px);opacity:0;pointer-events:none;background:#14233a;color:#fff;padding:10px 18px;border-radius:999px;font-size:13px;transition:.25s;z-index:40;max-width:calc(100% - 32px);text-align:center}
.toast.on{opacity:1;transform:translate(-50%,0)}

@media (max-width:900px){
  .hero{grid-template-columns:1fr;padding-top:28px}
}
@media (max-width:640px){
  .wrap{padding:0 16px}
  .lec-pair{grid-template-columns:1fr}
  .top .wrap{gap:8px}
  .top nav a{padding:6px 8px;font-size:13px}
  .brand small{display:none}
  .brand b{font-size:13px}
  .pager{grid-template-columns:1fr}
  .pager .next{grid-column:1}
  .file .acts{width:100%}
  .file .acts .btn{flex:1}
}
@media (max-width:400px){
  .brand-text{display:none}
}
@media (prefers-reduced-motion:reduce){*{transition:none!important}}