/* ============ 协议小白手册 · 终端机风格 ============ */
:root {
  --bg: #0e120c;
  --panel: #151b12;
  --panel-2: #1a2216;
  --line: #2c3a26;
  --green: #7ee787;
  --green-dim: #4c8a54;
  --amber: #ffb454;
  --red: #ff7b72;
  --cyan: #79c0ff;
  --txt: #d7e2cf;
  --txt-dim: #8b9a82;
  --mono: "JetBrains Mono", "Cascadia Code", Consolas, monospace;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--sans);
  background: var(--bg);
  color: var(--txt);
  line-height: 1.9;
  font-size: 16.5px;
  position: relative;
}
/* CRT 扫描线 */
body::after {
  content: "";
  position: fixed; inset: 0;
  background: repeating-linear-gradient(0deg, rgba(0,0,0,.14) 0 1px, transparent 1px 3px);
  pointer-events: none;
  z-index: 999;
}
body::before {
  content: "";
  position: fixed; inset: 0;
  background: radial-gradient(ellipse at 50% 0%, rgba(126,231,135,.06), transparent 60%);
  pointer-events: none;
  z-index: 0;
}
a { color: var(--green); text-decoration-color: var(--green-dim); text-underline-offset: 3px; }
a:hover { color: var(--amber); }
code, .chip { font-family: var(--mono); }
code {
  background: var(--panel-2); border: 1px solid var(--line);
  padding: 1px 7px; border-radius: 4px; font-size: .88em; color: var(--cyan);
}

/* ---------- 顶栏 ---------- */
.masthead {
  border-bottom: 1px solid var(--line);
  padding: 16px 5vw;
  display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 8px;
  background: rgba(14,18,12,.9); backdrop-filter: blur(4px);
  position: relative; z-index: 2;
}
.masthead .brand {
  font-family: var(--mono); font-weight: 700; font-size: 18px;
  color: var(--green); text-decoration: none;
}
.masthead .brand::before { content: "~/"; color: var(--txt-dim); }
.masthead .issue { font-family: var(--mono); font-size: 12px; color: var(--txt-dim); }
nav.toc {
  padding: 9px 5vw;
  border-bottom: 1px solid var(--line);
  display: flex; flex-wrap: wrap; gap: 3px 20px;
  font-size: 13.5px; font-family: var(--mono);
  position: sticky; top: 0; z-index: 50;
  background: rgba(14,18,12,.95); backdrop-filter: blur(4px);
}
nav.toc a { color: var(--txt-dim); text-decoration: none; }
nav.toc a::before { content: "> "; color: var(--green-dim); }
nav.toc a:hover, nav.toc a.active { color: var(--amber); }

/* ---------- 页头 ---------- */
.hero { padding: 9vh 5vw 6vh; border-bottom: 1px solid var(--line); position: relative; z-index: 1; }
.prompt {
  font-family: var(--mono); font-size: 14px; color: var(--txt-dim);
  margin-bottom: 24px; display: block;
}
.prompt b { color: var(--green); font-weight: 400; }
.prompt i { color: var(--amber); font-style: normal; }
h1.display {
  font-family: var(--mono); font-weight: 800;
  font-size: clamp(34px, 5.6vw, 64px);
  line-height: 1.22; letter-spacing: 0; max-width: 22em;
  color: #f0f6ec;
}
h1.display .hl { color: var(--green); }
h1.display .cursor { display: inline-block; width: .55em; height: 1.05em; background: var(--green); vertical-align: -.12em; animation: blink 1.1s steps(1) infinite; }
@keyframes blink { 50% { opacity: 0; } }
.standfirst {
  margin-top: 26px; max-width: 46em; font-size: 17.5px; color: var(--txt-dim);
  border-left: 3px solid var(--green-dim); padding-left: 18px;
}
.byline { margin-top: 20px; font-family: var(--mono); font-size: 12.5px; color: var(--txt-dim); }
.byline b { color: var(--txt); font-weight: 400; }

/* ---------- 正文 ---------- */
main.body { max-width: 880px; margin: 0 auto; padding: 60px 5vw 40px; position: relative; z-index: 1; }
section.chapter { margin-bottom: 72px; }
.chap-num { font-family: var(--mono); font-size: 13px; color: var(--green-dim); margin-bottom: 8px; letter-spacing: 2px; }
h2 {
  font-family: var(--mono); font-size: clamp(24px, 3vw, 32px);
  line-height: 1.35; margin-bottom: 20px; color: #f0f6ec;
}
h2::before { content: "## "; color: var(--green-dim); }
h3 { font-size: 19px; margin: 32px 0 12px; color: var(--amber); font-family: var(--mono); font-weight: 700; }
h3::before { content: "### "; color: var(--txt-dim); font-weight: 400; }
p { margin-bottom: 18px; }
main.body ul, main.body ol { padding-left: 1.6em; margin-bottom: 20px; }
main.body li { margin-bottom: 10px; }
main.body li::marker { color: var(--green); }
strong { color: #f0f6ec; font-weight: 700; }

/* 类比框 */
.analogy {
  margin: 30px 0; padding: 20px 24px; background: var(--panel);
  border: 1px solid var(--line); border-radius: 8px; position: relative;
}
.analogy::before {
  content: "🧠 用大白话类比"; position: absolute; top: -12px; left: 18px;
  background: var(--bg); padding: 0 10px; font-size: 12.5px; color: var(--amber);
  font-family: var(--mono); letter-spacing: 1px;
}
.analogy p { margin: 0; }

/* 终端窗口 */
.term {
  background: #0a0d08; border: 1px solid var(--line); border-radius: 8px;
  margin: 26px 0; overflow: hidden;
}
.term .bar {
  background: var(--panel-2); padding: 8px 14px; display: flex; gap: 6px; align-items: center;
  font-family: var(--mono); font-size: 12px; color: var(--txt-dim);
}
.term .bar::before { content: "● ● ●"; color: var(--line); letter-spacing: 3px; }
.term .bar span { margin-left: 8px; }
.term pre {
  padding: 16px 18px; font-family: var(--mono); font-size: 13.5px; line-height: 1.8;
  color: var(--txt); overflow-x: auto; white-space: pre;
}
.term .c-green { color: var(--green); } .term .c-amber { color: var(--amber); }
.term .c-cyan { color: var(--cyan); } .term .c-dim { color: var(--txt-dim); } .term .c-red { color: var(--red); }

/* 端口徽章 */
.port {
  display: inline-block; font-family: var(--mono); font-size: 12px;
  background: rgba(126,231,135,.1); border: 1px solid var(--green-dim);
  color: var(--green); padding: 1px 9px; border-radius: 999px; vertical-align: 2px;
  white-space: nowrap;
}

/* 表格 */
table { width: 100%; border-collapse: collapse; margin: 26px 0; font-size: 14.5px; }
th { background: var(--panel-2); color: var(--green); text-align: left; padding: 10px 14px; font-family: var(--mono); font-weight: 700; border-bottom: 2px solid var(--green-dim); }
td { border: 1px solid var(--line); padding: 10px 14px; vertical-align: top; background: var(--panel); }
td .m { font-family: var(--mono); color: var(--cyan); }

/* 步骤 */
ol.steps { counter-reset: step; list-style: none; padding: 0; }
ol.steps li {
  counter-increment: step; position: relative; padding: 16px 18px 16px 62px;
  border-left: 2px solid var(--line); margin: 0 0 4px;
}
ol.steps li::before {
  content: counter(step); position: absolute; left: -14px; top: 14px;
  font-family: var(--mono); font-weight: 700; font-size: 14px; color: var(--bg);
  background: var(--green); width: 28px; height: 28px; border-radius: 6px;
  display: flex; align-items: center; justify-content: center;
}
ol.steps li b { display: block; font-family: var(--mono); font-size: 16.5px; margin-bottom: 4px; color: #f0f6ec; }

/* FAQ */
.faq details { border-bottom: 1px solid var(--line); padding: 14px 4px; }
.faq summary { font-family: var(--mono); font-weight: 700; font-size: 16px; cursor: pointer; color: #f0f6ec; }
.faq summary::marker { color: var(--amber); }
.faq details p { margin: 12px 0 4px; color: var(--txt-dim); }

/* 交叉链接 */
.crosslinks { border-top: 1px solid var(--line); padding: 40px 0 10px; }
.crosslinks h2 { font-size: 22px; }
.link-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 14px; margin-top: 20px; }
.link-cards a {
  display: block; text-decoration: none; color: var(--txt);
  border: 1px solid var(--line); padding: 16px 18px; background: var(--panel); border-radius: 8px;
  transition: transform .15s ease, border-color .15s ease;
  font-family: var(--sans);
}
.link-cards a:hover { transform: translateY(-3px); border-color: var(--green); color: var(--txt); }
.link-cards .no { font-family: var(--mono); color: var(--green-dim); font-size: 12px; }
.link-cards .ti { font-family: var(--mono); font-weight: 700; font-size: 17px; margin: 6px 0; color: var(--green); }
.link-cards .de { font-size: 13px; color: var(--txt-dim); line-height: 1.6; }

/* 首页网格 */
.cover-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); gap: 16px; padding: 6vh 5vw; position: relative; z-index: 1; }
.cover-item {
  border: 1px solid var(--line); border-radius: 10px; padding: 26px 24px 22px;
  text-decoration: none; color: var(--txt); background: var(--panel);
  transition: border-color .2s, transform .2s; position: relative; overflow: hidden;
}
.cover-item::before {
  content: attr(data-port); position: absolute; right: 14px; top: 12px;
  font-family: var(--mono); font-size: 12px; color: var(--green-dim);
}
.cover-item:hover { border-color: var(--green); transform: translateY(-4px); }
.cover-item .no { font-family: var(--mono); font-size: 12px; color: var(--green-dim); letter-spacing: 2px; }
.cover-item h2 { font-family: var(--mono); font-size: 22px; margin: 8px 0 4px; color: var(--green); }
.cover-item h2::before { content: none; }
.cover-item .en { font-family: var(--mono); font-size: 12.5px; color: var(--amber); margin-bottom: 12px; }
.cover-item p { font-size: 14px; color: var(--txt-dim); margin: 0; line-height: 1.7; }

/* 页脚 */
footer {
  margin-top: 70px; border-top: 1px solid var(--line);
  padding: 26px 5vw 40px; font-size: 13px; color: var(--txt-dim); font-family: var(--mono);
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px;
  position: relative; z-index: 1;
}
footer nav a { margin-right: 16px; color: var(--txt-dim); }

@keyframes rise { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: none; } }
.hero > *, .cover-item, section.chapter > * { animation: rise .55s ease both; }
.hero > *:nth-child(2) { animation-delay: .07s; } .hero > *:nth-child(3) { animation-delay: .14s; } .hero > *:nth-child(4) { animation-delay: .21s; }
@media (prefers-reduced-motion: reduce) { * { animation: none !important; } }

@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .term pre { font-size: 12px; }
}