:root {
  --paper: #f3ede0;
  --paper-deep: #e9e0cd;
  --ink: #1b1916;
  --ink-soft: #4a443c;
  --muted: #7a7164;
  --line: #d6cab2;
  --cinnabar: #a4342a;
  --gold: #a98a56;
  --serif: "Noto Serif SC", "Songti SC", serif;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
  --radius: 2px;
  color-scheme: light;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--sans);
  color: var(--ink);
  background:
    radial-gradient(120% 80% at 12% 0%, #fbf7ee 0%, transparent 55%),
    radial-gradient(90% 70% at 100% 100%, #efe6d5 0%, transparent 60%),
    var(--paper);
}

.grain {
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.35;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.8' numOctaves='3'/%3E%3C/filter%3E%3Crect width='160' height='160' filter='url(%23n)' opacity='0.28'/%3E%3C/svg%3E");
  z-index: 0;
}

.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px clamp(16px, 4vw, 48px);
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}

.brand { display: flex; align-items: center; gap: 12px; }
.brand strong { font-family: var(--serif); font-size: 18px; letter-spacing: 0.08em; display: block; }
.brand small { color: var(--muted); font-size: 11px; letter-spacing: 0.22em; }

.seal {
  display: grid;
  place-items: center;
  width: 40px; height: 40px;
  color: #fdf8ee;
  background: var(--cinnabar);
  font-family: var(--serif);
  font-size: 20px;
  border-radius: 3px;
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.25);
}

.topbar-right { display: flex; align-items: center; gap: 12px; }
.who { font-size: 13px; color: var(--ink-soft); }

main {
  position: relative;
  z-index: 1;
  width: min(1240px, 100% - 32px);
  margin: 0 auto;
  padding: clamp(20px, 4vw, 44px) 0 80px;
}

.panel {
  background: color-mix(in srgb, #fffdf8 82%, transparent);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: clamp(18px, 2.4vw, 28px);
  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.6) inset, 0 18px 40px -32px rgba(60, 40, 20, 0.55);
}

.eyebrow {
  margin: 0 0 10px;
  font-size: 11px;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--cinnabar);
}

.muted { color: var(--muted); line-height: 1.75; font-size: 14px; margin: 0; }

.login-panel {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: clamp(24px, 5vw, 64px);
  align-items: center;
  min-height: 62vh;
}

.login-copy h1 {
  font-family: var(--serif);
  font-size: clamp(26px, 3.6vw, 40px);
  line-height: 1.3;
  margin: 0 0 14px;
  letter-spacing: 0.02em;
}

.steps { list-style: none; padding: 0; margin: 26px 0 0; display: grid; gap: 10px; }
.steps li {
  display: flex; align-items: center; gap: 10px;
  font-size: 13px; color: var(--ink-soft);
  padding-bottom: 10px; border-bottom: 1px dashed var(--line);
}
.steps span { font-family: var(--serif); color: var(--gold); font-size: 12px; letter-spacing: 0.12em; }

.login-form { display: grid; gap: 16px; }

label { display: grid; gap: 7px; font-size: 13px; color: var(--ink-soft); }

input, select, textarea {
  font: inherit;
  font-size: 14px;
  color: var(--ink);
  background: #fffdf7;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 11px 12px;
  width: 100%;
  transition: border-color 0.18s ease, box-shadow 0.18s ease;
}

input:focus-visible, select:focus-visible, textarea:focus-visible {
  outline: none;
  border-color: var(--gold);
  box-shadow: 0 0 0 3px rgba(169, 138, 86, 0.18);
}

.code-row { display: flex; gap: 8px; }
.code-row input { flex: 1; }

.btn {
  font: inherit;
  font-size: 14px;
  border-radius: var(--radius);
  border: 1px solid transparent;
  padding: 11px 18px;
  cursor: pointer;
  transition: transform 0.16s ease, background 0.18s ease, color 0.18s ease, border-color 0.18s ease;
  white-space: nowrap;
}
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn-primary { background: var(--ink); color: #f8f3e8; }
.btn-primary:hover:not(:disabled) { background: #2c2823; }
.btn-ghost { background: transparent; border-color: var(--line); color: var(--ink-soft); }
.btn-ghost:hover:not(:disabled) { border-color: var(--gold); color: var(--ink); }
.btn-small { padding: 7px 12px; font-size: 13px; }

.hint { margin: 0; font-size: 12px; color: var(--muted); min-height: 18px; }
.hint.is-error { color: var(--cinnabar); }
.hint.is-ok { color: #3f6b4a; }

.workspace { display: grid; gap: 18px; }

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}
.stat { background: #fffdf8; padding: 16px 18px; display: grid; gap: 6px; }
.stat span { font-size: 12px; color: var(--muted); letter-spacing: 0.08em; }
.stat strong { font-family: var(--serif); font-size: 26px; font-weight: 600; }

.split {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}

.panel-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 16px; }
.panel-head h2 { font-family: var(--serif); font-size: 18px; margin: 0; letter-spacing: 0.04em; }

.course-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; max-height: 60vh; overflow: auto; }
.course-item {
  width: 100%;
  text-align: left;
  background: transparent;
  border: 1px solid transparent;
  border-left: 2px solid var(--line);
  padding: 12px 14px;
  cursor: pointer;
  font: inherit;
  display: grid;
  gap: 4px;
  transition: background 0.16s ease, border-color 0.16s ease;
}
.course-item:hover { background: rgba(169, 138, 86, 0.08); }
.course-item.is-active { background: rgba(169, 138, 86, 0.14); border-left-color: var(--cinnabar); }
.course-item strong { font-size: 14px; font-weight: 600; }
.course-item small { color: var(--muted); font-size: 12px; }

.badge {
  display: inline-block;
  font-size: 11px;
  letter-spacing: 0.08em;
  padding: 2px 7px;
  border: 1px solid var(--line);
  color: var(--muted);
  border-radius: 999px;
}
.badge.is-live { border-color: #b9cdb9; color: #3f6b4a; background: #f2f7f0; }

.editor-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 18px;
}
.editor-head h2 { font-family: var(--serif); font-size: clamp(20px, 2.4vw, 26px); margin: 0 0 6px; }
.editor-actions { display: flex; gap: 8px; flex-wrap: wrap; }

.chapter { border: 1px solid var(--line); border-radius: var(--radius); margin-bottom: 12px; background: #fffdf8; }
.chapter-head {
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 12px 14px; border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(233, 224, 205, 0.5), transparent);
}
.chapter-head h3 { font-family: var(--serif); font-size: 15px; margin: 0; }
.chapter-body { padding: 10px 14px 14px; display: grid; gap: 8px; }

.lesson {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 8px;
  align-items: center;
  padding: 10px 0;
  border-bottom: 1px dashed var(--line);
  font-size: 13px;
}
.lesson:last-child { border-bottom: none; }
.lesson small { color: var(--muted); display: block; margin-top: 3px; }
.tag { font-size: 11px; color: var(--gold); border: 1px solid rgba(169, 138, 86, 0.4); padding: 1px 6px; margin-right: 6px; border-radius: 2px; }

.inline-form { display: flex; gap: 8px; margin-top: 14px; }
.inline-form input { flex: 1; }

.empty { display: grid; place-items: center; min-height: 240px; color: var(--muted); font-size: 14px; text-align: center; }

.upload-grid { display: grid; grid-template-columns: minmax(0, 1fr) 260px; gap: 18px; margin: 16px 0; }
.dropzone {
  border: 1px dashed var(--line);
  display: grid;
  place-items: center;
  gap: 8px;
  padding: 28px;
  cursor: pointer;
  background: rgba(255, 253, 247, 0.6);
}
.dropzone-title { font-family: var(--serif); color: var(--ink-soft); }
.dropzone input { border: none; background: transparent; padding: 0; font-size: 12px; }
.upload-meta { display: grid; gap: 12px; align-content: start; }

.progress { height: 4px; background: var(--paper-deep); overflow: hidden; }
.progress span { display: block; height: 100%; width: 0; background: var(--cinnabar); transition: width 0.2s ease; }

.media-list { list-style: none; padding: 0; margin: 8px 0 0; display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); max-height: 260px; overflow: auto; }
.media-list li { background: #fffdf8; padding: 10px 12px; font-size: 12px; display: flex; justify-content: space-between; gap: 12px; }
.media-list code { font-size: 11px; color: var(--muted); }

.dialog {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0;
  width: min(520px, calc(100% - 32px));
  background: #fffdf8;
  color: var(--ink);
  box-shadow: 0 40px 80px -40px rgba(40, 26, 12, 0.6);
}
.dialog::backdrop { background: rgba(27, 25, 22, 0.45); backdrop-filter: blur(2px); }
.dialog-body { padding: 24px; display: grid; gap: 14px; }
.dialog-body h2 { font-family: var(--serif); margin: 0; font-size: 20px; }
.dialog-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 6px; }

.toast {
  position: fixed;
  left: 50%;
  bottom: 28px;
  transform: translate(-50%, 20px);
  background: var(--ink);
  color: #f8f3e8;
  padding: 11px 20px;
  font-size: 13px;
  border-radius: var(--radius);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.22s ease, transform 0.22s ease;
  max-width: calc(100% - 32px);
}
.toast.is-visible { opacity: 1; transform: translate(-50%, 0); }

@media (max-width: 900px) {
  .login-panel { grid-template-columns: 1fr; min-height: auto; }
  .split { grid-template-columns: 1fr; }
  .upload-grid { grid-template-columns: 1fr; }
  .editor-head { flex-direction: column; }
}

@media (max-width: 520px) {
  main { width: calc(100% - 24px); }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .inline-form { flex-direction: column; }
  .code-row { flex-direction: column; }
}