/* Next Payment — MCP documentation. Self-contained; mirrors the marketing site's tokens. */
:root{
  --text-xs:clamp(.75rem,.72rem + .15vw,.8125rem);
  --text-sm:clamp(.875rem,.84rem + .2vw,.9375rem);
  --text-base:clamp(1rem,.96rem + .2vw,1.0625rem);
  --text-lg:clamp(1.125rem,1.02rem + .5vw,1.375rem);
  --text-xl:clamp(1.5rem,1.2rem + 1.1vw,2.125rem);
  --text-2xl:clamp(2rem,1.3rem + 2.4vw,3.25rem);
  --space-1:.25rem; --space-2:.5rem; --space-3:.75rem; --space-4:1rem; --space-5:1.25rem;
  --space-6:1.5rem; --space-8:2rem; --space-10:2.5rem; --space-12:3rem; --space-16:4rem; --space-20:5rem;
  --bg:#f6f7f9; --surface:#fff; --surface-2:#fbfcfd;
  /* --faint carries .muted body copy and table headings. #6c7585 measured
     4.33:1 on the canvas, under the 4.5:1 floor for normal text; this is
     5.33:1. Darkened rather than reassigned so the hierarchy is unchanged. */
  --text:#0b0d12; --muted:#3c4350; --faint:#5f6774;
  /* --accent-ink is drawn on --accent-soft by .tag; #0a7b4d measured 4.44:1
     there. Kept in step with site/style.css. */
  --accent:#0f9d63; --accent-soft:rgba(15,157,99,.10); --accent-ink:#0a7549;
  --line:#e6e9ee; --line-2:#eef1f5; --code-bg:#fbfcfd;
  --r-sm:10px; --r-md:14px; --r-lg:16px; --r-xl:22px;
  --shadow-s:0 1px 2px rgba(11,13,18,.04),0 1px 12px rgba(11,13,18,.03);
  --shadow-m:0 2px 6px rgba(11,13,18,.05),0 18px 44px -22px rgba(11,13,18,.16);
  --shell:1180px; --header-h:68px;
  --font-display:"Inter",ui-sans-serif,system-ui,-apple-system,"Segoe UI","Noto Sans TC",sans-serif;
  --font-body:"Inter",ui-sans-serif,system-ui,-apple-system,"Segoe UI","Noto Sans TC",sans-serif;
  --font-mono:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
  --ease:cubic-bezier(.22,.61,.36,1);
}
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font-family:var(--font-body);
  font-size:var(--text-base);line-height:1.6;-webkit-font-smoothing:antialiased}
a{color:var(--accent-ink);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3{font-family:var(--font-display);font-weight:500;letter-spacing:-.022em;line-height:1.15;margin:0}
p{margin:0}
.shell{width:100%;max-width:var(--shell);margin-inline:auto;padding-inline:var(--space-6)}
.mono{font-family:var(--font-mono);font-size:var(--text-xs);letter-spacing:.02em}
.muted{color:var(--faint)}

/* header */
.site-header{position:sticky;top:0;z-index:30;background:color-mix(in srgb,var(--bg) 88%,transparent);
  backdrop-filter:blur(12px);border-bottom:1px solid var(--line)}
.site-header-inner{display:flex;align-items:center;gap:var(--space-5);height:var(--header-h)}
.brand{display:flex;align-items:center;gap:9px;color:var(--text);margin-right:auto}
/* Same mark as the landing and the marketing site: a light square with the
   brand arrow. The old dark square held a white "H", which made the docs read
   as a different company. */
.brand-mark{width:30px;height:30px;border-radius:9px;background:var(--surface);border:1px solid var(--line);display:grid;place-items:center;flex:none}
.brand-rule{width:1px;height:22px;background:var(--line);margin-inline:4px}
.brand-name{font-family:var(--font-display);font-weight:600;font-size:1rem;letter-spacing:-.02em}
.brand-by{font-family:var(--font-mono);font-size:.625rem;color:var(--faint);letter-spacing:.03em;display:block}
.top-nav{display:flex;align-items:center;gap:var(--space-5);font-size:var(--text-sm)}
.top-nav a{color:var(--muted)}
/* Keep button colours from being overridden by the nav link colour. */
.top-nav a.btn-primary{color:#fff}
.top-nav a.btn-primary:hover{color:#fff}
.lang{padding:5px 10px;border:1px solid var(--line);border-radius:999px;background:var(--surface)}
.lang a{color:var(--muted)} .lang a[aria-current="true"]{color:var(--text);font-weight:600}
.btn{display:inline-flex;align-items:center;gap:8px;border-radius:999px;padding:10px 18px;
  font-size:var(--text-sm);font-weight:600;border:1px solid transparent;transition:transform .16s var(--ease),opacity .16s}
.btn:hover{text-decoration:none;transform:translateY(-1px)}
.btn-primary{background:var(--text);color:#fff}
.btn-ghost{background:var(--surface);border-color:var(--line);color:var(--text)}

/* layout */
.layout{display:grid;grid-template-columns:236px minmax(0,1fr);gap:var(--space-12);
  padding-block:var(--space-10) var(--space-20);align-items:start}
.side{position:sticky;top:calc(var(--header-h) + 24px);display:flex;flex-direction:column;gap:2px}
.side .side-label{font-family:var(--font-mono);font-size:.625rem;text-transform:uppercase;letter-spacing:.12em;
  color:var(--faint);padding:0 12px 8px}
.side a{display:block;padding:7px 12px;border-radius:var(--r-sm);color:var(--muted);font-size:var(--text-sm)}
.side a:hover{background:var(--surface);color:var(--text);text-decoration:none}
.main{min-width:0;display:flex;flex-direction:column;gap:var(--space-16)}
section{scroll-margin-top:calc(var(--header-h) + 24px)}

/* hero */
.hero{display:flex;flex-direction:column;gap:var(--space-5);max-width:44rem}
.eyebrow{font-family:var(--font-mono);font-size:var(--text-xs);letter-spacing:.08em;text-transform:uppercase;color:var(--accent-ink)}
.hero h1{font-size:var(--text-2xl)}
.hero .lede{font-size:var(--text-lg);color:var(--muted)}
.hero-actions{display:flex;gap:var(--space-3);flex-wrap:wrap}

/* flow diagram */
.flow{margin-top:var(--space-2);background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r-xl);box-shadow:var(--shadow-s);padding:var(--space-8)}
.flow-track{display:grid;grid-template-columns:1fr auto 1fr auto 1fr;gap:var(--space-3);align-items:stretch}
.flow-node{background:var(--surface-2);border:1px solid var(--line);border-radius:var(--r-lg);
  padding:var(--space-5);display:flex;flex-direction:column;gap:6px;justify-content:flex-start}
.flow-node .n{font-family:var(--font-mono);font-size:.625rem;letter-spacing:.1em;color:var(--faint)}
.flow-node h3{font-size:var(--text-base);font-family:var(--font-body);font-weight:600;letter-spacing:0}
.flow-node p{font-size:var(--text-sm);color:var(--faint)}
.flow-arrow{display:grid;place-items:center;color:var(--faint)}
.flow-arrow svg{width:22px;height:22px}
.flow-drop{display:grid;place-items:center;margin:var(--space-4) 0}
.flow-final{background:var(--accent-soft);border:1px solid color-mix(in srgb,var(--accent) 35%,var(--line));
  border-radius:var(--r-lg);padding:var(--space-5);display:flex;gap:var(--space-4);align-items:center}
.flow-final strong{font-weight:600}
.never{display:flex;gap:8px;flex-wrap:wrap;margin-top:var(--space-4)}
.chip{font-family:var(--font-mono);font-size:.5625rem;letter-spacing:.06em;text-transform:uppercase;
  padding:4px 10px;border-radius:999px;border:1px dashed var(--line);color:var(--faint)}

/* cards / grids */
.grid-2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:var(--space-5)}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-lg);padding:var(--space-6);
  box-shadow:var(--shadow-s)}
.card h3{font-size:var(--text-base);font-family:var(--font-body);font-weight:600;letter-spacing:0;margin-bottom:8px}
.list{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:9px}
.list li{display:flex;gap:10px;font-size:var(--text-sm);color:var(--muted)}
.list li::before{content:"";width:6px;height:6px;border-radius:50%;background:var(--accent);flex:none;margin-top:9px}
.list.no li::before{background:var(--faint)}
.section-head{display:flex;flex-direction:column;gap:8px;margin-bottom:var(--space-6)}
.section-head h2{font-size:var(--text-xl)}
.section-head p{color:var(--muted);max-width:62ch}

/* server url + copy */
.url-bar{display:flex;align-items:center;gap:var(--space-3);background:var(--surface-2);
  border:1px solid var(--line);border-radius:var(--r-md);padding:6px 6px 6px 14px;max-width:560px}
.url-bar code{font-family:var(--font-mono);font-size:var(--text-sm);color:var(--text);flex:1;
  overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.copy{display:inline-flex;align-items:center;gap:6px;background:var(--text);color:#fff;border:0;
  border-radius:999px;padding:7px 14px;font-size:var(--text-xs);font-weight:600;cursor:pointer;
  font-family:var(--font-body)}
.copy.copied{background:var(--accent)}

/* client tabs */
.tabs{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:var(--space-5)}
.tab{background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:8px 15px;
  font-size:var(--text-sm);font-weight:600;color:var(--muted);cursor:pointer}
.tab[aria-selected="true"]{background:var(--text);border-color:var(--text);color:#fff}
.panel[hidden]{display:none}
.steps{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:var(--space-4);counter-reset:s}
.steps li{display:grid;grid-template-columns:26px 1fr;gap:12px;align-items:start;font-size:var(--text-sm)}
.steps li::before{counter-increment:s;content:counter(s);width:26px;height:26px;border-radius:50%;
  border:1px solid var(--line);display:grid;place-items:center;font-family:var(--font-mono);font-size:var(--text-xs);color:var(--faint)}
.code{background:var(--code-bg);border:1px solid var(--line-2);border-radius:var(--r-md);
  padding:12px 14px;margin-top:8px;display:flex;gap:12px;align-items:flex-start}
.code pre{margin:0;font-family:var(--font-mono);font-size:var(--text-xs);color:var(--muted);
  white-space:pre-wrap;overflow-wrap:anywhere;flex:1}

/* tools table */
table.tools{width:100%;border-collapse:collapse;background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r-lg);overflow:hidden;font-size:var(--text-sm)}
.tools-scroll{overflow-x:auto;-webkit-overflow-scrolling:touch;border-radius:var(--r-lg)}
.tools-scroll table.tools{min-width:520px}
table.tools th,table.tools td{text-align:left;padding:12px 16px;border-bottom:1px solid var(--line-2)}
table.tools th{font-family:var(--font-mono);font-size:.625rem;text-transform:uppercase;letter-spacing:.1em;color:var(--faint);font-weight:500}
table.tools tr:last-child td{border-bottom:0}
table.tools code{font-family:var(--font-mono);font-size:var(--text-xs);color:var(--text)}
.tag{font-family:var(--font-mono);font-size:.75rem;letter-spacing:.06em;text-transform:uppercase;
  padding:2px 8px;border-radius:999px;background:var(--accent-soft);color:var(--accent-ink)}
/* 5.27:1 on --line-2 (AA needs 4.5:1); --faint was 4.10:1. */
.tag.next{background:var(--line-2);color:#5b6473}

/* cta + footer */
.cta{background:var(--text);color:#fff;border-radius:var(--r-xl);padding:var(--space-10);
  display:flex;gap:var(--space-5);align-items:center;justify-content:space-between;flex-wrap:wrap}
.cta h2{font-size:var(--text-xl);color:#fff}
.cta p{color:rgba(255,255,255,.72);font-size:var(--text-sm);margin-top:6px;max-width:46ch}
.cta .btn-primary{background:#fff;color:var(--text)}
.cta .btn-ghost{background:transparent;border-color:rgba(255,255,255,.32);color:#fff}
.site-footer{border-top:1px solid var(--line);margin-top:var(--space-20);padding-block:var(--space-8);
  font-size:var(--text-xs);color:var(--faint)}
.site-footer .footer-legal{margin:10px 0 0}
.site-footer .footer-legal a{color:var(--muted);text-decoration:underline}

@media(max-width:980px){
  .layout{grid-template-columns:1fr;gap:var(--space-8)}
  .side{position:static;flex-direction:row;flex-wrap:wrap;gap:6px}
  .side .side-label{display:none}
  .flow-track{grid-template-columns:1fr;gap:8px}
  .flow-arrow{transform:rotate(90deg)}
  .grid-2{grid-template-columns:1fr}
}
@media(prefers-reduced-motion:reduce){*{transition:none !important;scroll-behavior:auto}}

/* ==========================================================================
   Three-column reading layout with a live code panel (readme.io style)
   ========================================================================== */
.layout{grid-template-columns:212px minmax(0,1fr) 348px;gap:var(--space-8)}
.panel-col{position:sticky;top:calc(var(--header-h) + 24px)}
.doc-panel{background:#0d1117;border-radius:var(--r-lg);overflow:hidden;
  box-shadow:0 24px 60px -34px rgba(11,13,18,.55),0 2px 6px rgba(11,13,18,.16)}
.doc-panel-head{display:flex;align-items:center;gap:8px;padding:11px 14px;
  background:rgba(255,255,255,.04);border-bottom:1px solid rgba(255,255,255,.08)}
.doc-panel-head .dot{width:8px;height:8px;border-radius:50%;background:#3f4753;flex:none}
.doc-panel-head .dot:first-child{background:#5a6472}
.doc-panel-title{font-family:var(--font-mono);font-size:.6875rem;color:#8b949e;margin-left:4px;
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.doc-panel-live{margin-left:auto;font-family:var(--font-mono);font-size:.5625rem;color:#3fb950;
  border:1px solid rgba(63,185,80,.35);border-radius:999px;padding:2px 8px}
.doc-panel-body{padding:16px;max-height:min(62vh,540px);overflow:auto}
.doc-panel-body pre{margin:0;font-family:var(--font-mono);font-size:.75rem;line-height:1.7;
  color:#c9d1d9;white-space:pre-wrap;overflow-wrap:anywhere}
.doc-panel-body pre .c{color:#8b949e}
.doc-panel-body pre .k{color:#ff7b72}
.doc-panel-body pre .s{color:#a5d6ff}
.doc-panel-body pre .g{color:#7ee787}
.doc-panel-body pre .n{color:#d2a8ff}
.doc-panel-body pre[hidden]{display:none}
/* 10px on #0d1117 needs 4.5:1; #6e7681 was 4.12:1, #8b949e is 6.15:1 and is
   the same tone the panel head already uses. */
.doc-panel-foot{padding:10px 14px;border-top:1px solid rgba(255,255,255,.08);
  font-family:var(--font-mono);font-size:.625rem;color:#8b949e}
.panel-hint{font-size:var(--text-xs);color:var(--faint);margin-top:10px;text-align:center}

/* before you start */
.checklist{display:grid;gap:var(--space-3);counter-reset:c}
.checklist li{display:grid;grid-template-columns:26px 1fr;gap:12px;align-items:start;
  background:var(--surface);border:1px solid var(--line);border-radius:var(--r-md);
  padding:var(--space-5);font-size:var(--text-sm);list-style:none}
.checklist li::before{counter-increment:c;content:counter(c);width:26px;height:26px;border-radius:50%;
  background:var(--accent-soft);color:var(--accent-ink);display:grid;place-items:center;
  font-family:var(--font-mono);font-size:var(--text-xs);font-weight:600}
.checklist strong{display:block;font-weight:600;margin-bottom:2px}
.checklist p{color:var(--muted)}

/* architecture diagram */
.arch{margin-top:var(--space-2);background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r-xl);box-shadow:var(--shadow-s);padding:var(--space-6)}
.arch-sides{display:grid;grid-template-columns:minmax(0,1fr) auto minmax(0,2.1fr);gap:var(--space-4);align-items:stretch}
.arch-side{border:1px solid var(--line);border-radius:var(--r-lg);padding:var(--space-5);background:var(--surface-2)}
.arch-side .arch-label{font-family:var(--font-mono);font-size:.5625rem;letter-spacing:.12em;
  text-transform:uppercase;color:var(--faint);display:block;margin-bottom:12px}
.arch-boundary{width:0;border-left:1.5px dashed var(--line);position:relative;display:grid;place-items:center}
.arch-boundary span{position:absolute;background:var(--bg);padding:6px 4px;font-family:var(--font-mono);
  font-size:.5rem;letter-spacing:.1em;text-transform:uppercase;color:var(--faint);writing-mode:vertical-rl}
.arch-col{display:grid;gap:10px}
.arch-box{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-md);padding:12px 14px;font-size:var(--text-sm)}
.arch-box b{font-weight:600}
.arch-box span{display:block;color:var(--faint);font-size:var(--text-xs);margin-top:2px}
.arch-arrow{display:grid;place-items:center;color:var(--faint)}
.arch-arrow svg{width:18px;height:18px;transform:rotate(90deg)}

/* workflows */
.wf{display:grid;gap:var(--space-4)}
.wf-row{display:grid;grid-template-columns:1fr;gap:6px;background:var(--surface);
  border:1px solid var(--line);border-radius:var(--r-lg);padding:var(--space-5)}
.wf-row h3{font-size:var(--text-base);font-family:var(--font-body);font-weight:600;letter-spacing:0}
.wf-row .ask{font-size:var(--text-sm);color:var(--muted);font-style:italic}
.wf-steps{display:flex;flex-wrap:wrap;gap:8px;margin-top:6px}
.wf-step{font-family:var(--font-mono);font-size:.625rem;color:var(--muted);
  background:var(--line-2);border-radius:999px;padding:4px 10px}

/* faq */
.faq{display:grid;gap:var(--space-3)}
.faq details{background:var(--surface);border:1px solid var(--line);border-radius:var(--r-md);
  padding:var(--space-4) var(--space-5)}
.faq summary{cursor:pointer;font-weight:600;font-size:var(--text-sm);list-style:none}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"+";float:right;color:var(--faint);font-family:var(--font-mono)}
.faq details[open] summary::after{content:"–"}
.faq p{color:var(--muted);font-size:var(--text-sm);margin-top:10px}

/* Tablet and narrow desktop only — must not apply on phones (the 980px rule below wins there). */
@media(min-width:981px) and (max-width:1180px){
  .layout{grid-template-columns:200px minmax(0,1fr)}
  .panel-col{display:none}
}
@media(max-width:980px){
  .arch-sides{grid-template-columns:1fr}
  .arch-boundary{width:100%;border-left:0;border-top:1.5px dashed var(--line);height:0}
  .arch-boundary span{writing-mode:horizontal-tb;padding:0 8px}
  .arch-arrow svg{transform:none}
}

/* Phone layout — kept last so it wins over the three-column rules above. */
@media(max-width:980px){
  .layout{grid-template-columns:1fr;gap:var(--space-8)}
  .side{position:static;flex-direction:row;flex-wrap:wrap;gap:6px}
  .side .side-label{display:none}
  .panel-col{display:none}
  .doc-panel-body{max-height:none}
}