/* ============================================================
   期权笔记 — Swiss journal
   tokens: #FFFFFF surface · #111 ink · #FF4F00 accent · hairline #E3E3E8
   type: Helvetica Neue + PingFang/Noto Sans SC — one sans family
   ============================================================ */
:root{
  --bg:#FFFFFF;
  --ink:#111111;
  --ink2:#6E6E76;
  --line:#E3E3E8;
  --neutral:#F7F7F8;
  --rule:#111111;
  --ac:#FF4F00;
  --sans:"Helvetica Neue",Helvetica,"PingFang SC","Noto Sans SC","Source Han Sans SC","Microsoft YaHei",Arial,sans-serif;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.85 var(--sans);font-synthesis:none}
::selection{background:var(--ac);color:#fff}

a{color:var(--ink);text-decoration:underline;text-decoration-color:var(--ac);text-decoration-thickness:2px;text-underline-offset:3px}
a:hover{color:var(--ac)}

/* ---- flag bar ---- */
.flag{height:8px;background:var(--rule)}

/* ---- masthead ---- */
.site-head{max-width:960px;margin:0 auto;padding:26px 24px 16px;
  display:flex;align-items:flex-end;justify-content:space-between;gap:16px;
  border-bottom:2px solid var(--rule)}
.site-title{font-size:1.65rem;font-weight:700;line-height:1.2;letter-spacing:.01em;color:var(--ink);text-decoration:none}
.site-title:hover{color:var(--ac);text-decoration:none}
.site-tag{color:var(--ink2);font-size:.78rem;line-height:1.6;text-align:right;letter-spacing:.08em;padding-bottom:3px}

main{max-width:960px;margin:0 auto;padding:0 24px 64px}

/* ---- folio lines ---- */
.folio{display:flex;justify-content:space-between;gap:12px;
  color:var(--ink2);font-size:.76rem;letter-spacing:.1em;
  padding:13px 0;border-bottom:1px solid var(--line)}

/* ---- journal index ---- */
.post-list{margin:0}
.post-item{display:grid;grid-template-columns:118px 1fr auto;gap:22px;align-items:start;
  padding:28px 0;border-bottom:1px solid var(--line);text-decoration:none}
.post-num{font-size:3.6rem;font-weight:700;line-height:.9;letter-spacing:-.02em;color:var(--ink)}
.post-item-title{display:block;color:var(--ink);font-weight:700;font-size:1.18rem;line-height:1.55;margin-top:4px}
.post-item:hover .post-num{color:var(--ac)}
.post-item:hover .post-item-title{color:var(--ink);text-decoration:underline;text-decoration-color:var(--ac);text-decoration-thickness:3px;text-underline-offset:7px}
.post-item-date{color:var(--ink2);font-size:.76rem;letter-spacing:.1em;white-space:nowrap;padding-top:8px}

/* ---- article ---- */
.art-num{font-size:clamp(4.6rem,14vw,8.6rem);font-weight:700;line-height:1;letter-spacing:-.03em;color:var(--ac);margin:34px 0 0}
.post-title{font-size:clamp(1.6rem,4.5vw,2.3rem);line-height:1.35;font-weight:700;margin:10px 0 8px;max-width:22em}
.post-meta{color:var(--ink2);font-size:.78rem;letter-spacing:.1em;margin:0;padding-bottom:26px;border-bottom:2px solid var(--rule)}

article{max-width:720px}
article h2{font-size:1.3rem;margin:2.5em 0 .8em;line-height:1.4}
article h3{font-size:1.08rem;margin:2em 0 .6em}
article p{margin:1em 0}
article img{max-width:100%}
article hr{border:0;border-top:1px solid var(--line);margin:2.5em 0}
article table{border-collapse:collapse;width:100%;margin:1.5em 0;font-size:.92rem}
article th{border-top:2px solid var(--rule);border-bottom:1px solid var(--rule);padding:8px 10px;text-align:left;font-weight:700}
article td{border-bottom:1px solid var(--line);padding:8px 10px}
article code{background:var(--neutral);border:1px solid var(--line);padding:1px 5px;font-size:.88em;font-family:"SF Mono",Consolas,"Liberation Mono","Courier New",monospace}
article pre{background:var(--neutral);border:1px solid var(--line);padding:16px;overflow-x:auto;font-size:.84rem;line-height:1.6}
article pre code{background:none;border:0;padding:0}
article blockquote{margin:1.4em 0;padding-left:16px;border-left:3px solid var(--rule);color:var(--ink2)}
.katex-display{margin:1.5em 0;padding:2px 0;overflow-x:auto;overflow-y:hidden}

/* ---- prev / next ---- */
.pn{display:grid;grid-template-columns:1fr 1fr;border-top:2px solid var(--rule);margin-top:56px}
.pn a{padding:16px 4px 0;text-decoration:none}
.pn .next{text-align:right}
.pn .lbl{color:var(--ink2);font-size:.76rem;letter-spacing:.1em}
.pn strong{display:block;font-weight:700;font-size:.95rem;line-height:1.5;margin-top:4px}
.pn a:hover strong{color:var(--ac);text-decoration:underline;text-decoration-color:var(--ac);text-decoration-thickness:2px;text-underline-offset:4px}

/* ---- footer ---- */
.site-foot{max-width:960px;margin:0 auto;padding:18px 24px;border-top:1px solid var(--line);
  display:flex;justify-content:space-between;gap:12px;
  color:var(--ink2);font-size:.76rem;letter-spacing:.1em}
.site-foot a{color:var(--ink2)}

.author-note{margin-top:36px;padding:16px 0 0;border-top:2px solid var(--rule);display:flex;justify-content:space-between;gap:16px;align-items:baseline}
.author-note .who{font-size:.78rem;letter-spacing:.1em;font-weight:700;white-space:nowrap}
.author-note .bio{color:var(--ink2);font-size:.85rem;line-height:1.6;max-width:56ch;text-align:right}
.author-note .bio a{color:var(--ink);text-decoration-color:var(--ac);text-decoration-thickness:2px;text-underline-offset:4px}
/* ---- responsive ---- */
@media (max-width:640px){
  .site-head{flex-direction:column;align-items:flex-start;gap:6px;padding-top:22px}
  .site-tag{text-align:left}
  .post-item{grid-template-columns:1fr;gap:8px;padding:22px 0}
  .post-num{font-size:2.7rem}
  .post-item-date{padding-top:0}
  .pn{grid-template-columns:1fr}
  .pn .next{text-align:left;border-top:1px solid var(--line);padding-top:12px}
  .author-note{flex-direction:column;gap:6px}
  .author-note .bio{text-align:left}
}