/* 第4套：步骤驱动 · 左侧固定导轨 · 暖灰底 + 森林绿 + 锈色按钮 */
:root {
  --bg: #e8e4dc;
  --rail: #24362b;
  --paper: #f6f3ec;
  --ink: #1f2a24;
  --green: #2f5d3a;
  --rust: #c2410c;
  --rust-ink: #fff7f2;
  --mute: #5c685f;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Trebuchet MS", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.7;
}

.shell {
  display: grid;
  grid-template-columns: 230px 1fr;
  min-height: 100vh;
}
.rail {
  background: var(--rail);
  color: #e7efe8;
  padding: 28px 20px 40px;
  position: sticky;
  top: 0;
  height: 100vh;
}
.brand {
  color: #e7efe8;
  text-decoration: none;
  font-size: 26px;
  font-weight: 700;
  letter-spacing: 0.08em;
  display: flex;
  align-items: center;
  gap: 8px;
}
.rail nav { margin-top: 36px; display: flex; flex-direction: column; gap: 6px; }
.rail nav a {
  color: #c5d2c8;
  text-decoration: none;
  padding: 10px 12px;
  border-left: 3px solid transparent;
}
.rail nav a.here {
  background: #31553c;
  color: #fff;
  border-left-color: #e0b089;
}

.stage { padding: 0 0 48px; }
.hero-step {
  background: var(--paper);
  padding: 40px 40px 32px;
  border-bottom: 6px solid var(--green);
}
.hero-step h1 { margin: 0 0 12px; font-size: 28px; line-height: 1.35; color: var(--green); }
.btn-rust {
  display: inline-block;
  background: var(--rust);
  color: var(--rust-ink);
  text-decoration: none;
  padding: 12px 18px;
  font-weight: 700;
}
.btn-plain {
  display: inline-block;
  margin-left: 10px;
  padding: 11px 16px;
  border: 1px solid var(--green);
  color: var(--green);
  text-decoration: none;
}

.step-block {
  margin: 28px 40px 0;
  background: var(--paper);
  padding: 24px 28px 28px;
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: 16px;
}
.step-block .tick {
  font-size: 40px;
  font-weight: 700;
  color: var(--green);
  line-height: 1;
}
.step-block h2 { margin: 0 0 10px; font-size: 20px; color: var(--green); }

ol.tight { margin: 0; padding-left: 20px; }
ol.tight li { margin: 8px 0; }

dl.ask dt { margin-top: 14px; font-weight: 700; }
dl.ask dd { margin: 6px 0 0; color: var(--mute); }

.base {
  margin: 28px 40px 0;
  color: var(--mute);
  font-size: 13px;
}
.base a { color: var(--green); margin-right: 12px; }

@media (max-width: 860px) {
  .shell { grid-template-columns: 1fr; }
  .rail { position: relative; height: auto; }
  .rail nav { flex-direction: row; flex-wrap: wrap; margin-top: 16px; }
  .hero-step, .step-block, .base { margin-left: 16px; margin-right: 16px; padding-left: 20px; padding-right: 20px; }
  .hero-step { margin: 0; }
  .btn-plain { margin-left: 0; margin-top: 8px; }
  .step-block { grid-template-columns: 1fr; }
}