/* 只用系统字体，不引任何外部资源 */
:root {
  --bg: #f6f6f3; --card: #fff; --ink: #1f2328; --muted: #67707a; --line: #dedfdb;
  --accent: #175C43; --accent-soft: #e3efe9; --warn: #a15c00; --warn-soft: #fdf1df;
  --bad: #b42318; --bad-soft: #fde8e6; --mark: #fff0b3; --mark-on: #ffd84d;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #151716; --card: #1f2221; --ink: #e7e9e7; --muted: #9aa19d; --line: #333836;
    --accent: #4fb38a; --accent-soft: #1d3329; --warn: #e3a54a; --warn-soft: #3a2d17;
    --bad: #f07167; --bad-soft: #3d1f1d; --mark: #5a4a12; --mark-on: #8a6d0b;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
}
a { color: var(--accent); }
.top {
  position: sticky; top: 0; z-index: 5; display: flex; align-items: center; justify-content: space-between;
  gap: 12px; padding: 10px 16px; background: var(--accent); color: #fff;
}
.top .brand { color: #fff; font-weight: 700; text-decoration: none; font-size: 17px; }
#who { font-size: 14px; display: flex; gap: 10px; align-items: center; min-width: 0; }
#who span { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
#who button { flex: none; min-height: 30px; background: transparent; color: #fff; border: 1px solid rgba(255,255,255,.6); padding: 2px 10px; font-size: 13px; font-weight: 500; border-radius: 6px; }
main { max-width: 760px; margin: 0 auto; padding: 16px 16px 120px; }
h1 { font-size: 21px; line-height: 1.35; margin: 4px 0 6px; }
h2 { font-size: 17px; margin: 22px 0 10px; }
.muted { color: var(--muted); }
.small { font-size: 14px; }
.center { text-align: center; }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; margin-bottom: 12px;
}

/* 表单 */
label { display: block; font-size: 14px; color: var(--muted); margin: 0 0 6px; }
input, textarea, select {
  width: 100%; font: inherit; color: var(--ink); background: var(--card);
  border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px;
}
input:focus, textarea:focus { outline: 2px solid var(--accent); outline-offset: -1px; border-color: transparent; }
.field { margin-bottom: 14px; }
button, .btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  font: inherit; font-weight: 600; min-height: 44px; padding: 10px 18px; border-radius: 8px;
  border: 1px solid var(--accent); background: var(--accent); color: #fff; cursor: pointer;
}
button.ghost { background: transparent; color: var(--accent); }
button:disabled { opacity: .5; cursor: default; }
button.full { width: 100%; }
.seg { display: flex; gap: 10px; }
.seg button { flex: 1; background: var(--card); color: var(--ink); border-color: var(--line); }
.seg button.on { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }
.err { color: var(--bad); font-size: 14px; min-height: 1.4em; margin: 8px 0 0; }
.login { max-width: 420px; margin: 24px auto 0; }

/* 作业列表 */
.item { display: block; text-decoration: none; color: inherit; }
.item:active { background: var(--accent-soft); }
.item .row1 { display: flex; justify-content: space-between; align-items: flex-start; gap: 10px; }
.item .t { font-weight: 600; font-size: 16px; overflow-wrap: anywhere; }
.item .meta { font-size: 14px; color: var(--muted); margin-top: 4px; }
.badge {
  flex: none; font-size: 13px; font-weight: 600; padding: 2px 9px; border-radius: 999px; white-space: nowrap;
  background: var(--line); color: var(--ink);
}
.badge.todo { background: var(--warn-soft); color: var(--warn); }
.badge.returned, .badge.overdue { background: var(--bad-soft); color: var(--bad); }
.badge.submitted { background: var(--line); color: var(--muted); }
.badge.reviewed { background: var(--accent-soft); color: var(--accent); }
.late { color: var(--bad); }

/* 作业页 */
.back { display: inline-block; margin-bottom: 6px; font-size: 15px; text-decoration: none; }
.prompt { white-space: pre-wrap; overflow-wrap: anywhere; font-family: Georgia, "Times New Roman", serif; font-size: 16px; line-height: 1.6; }
.prompt + .prompt { margin-top: 8px; }
.charts img { display: block; max-width: 100%; height: auto; margin: 10px auto 0; border-radius: 6px; background: #fff; }
.charts a { display: block; }
.note { background: var(--warn-soft); color: var(--ink); border-radius: 8px; padding: 10px 12px; margin: 10px 0 0; font-size: 15px; }
.banner { border-radius: 10px; padding: 10px 14px; margin: 0 0 12px; font-size: 15px; }
.banner.ok { background: var(--accent-soft); }
.banner.warn { background: var(--warn-soft); }
.banner.bad { background: var(--bad-soft); }
.banner button { min-height: 34px; padding: 4px 12px; margin-top: 6px; font-size: 14px; }
textarea.essay {
  min-height: 55vh; resize: vertical; line-height: 1.7; font-size: 16px;
  font-family: Georgia, "Times New Roman", serif;
}
.bar {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 6; background: var(--card); border-top: 1px solid var(--line);
  padding: 8px 16px calc(8px + env(safe-area-inset-bottom));
}
.bar .in { max-width: 1240px; margin: 0 auto; display: flex; align-items: center; gap: 10px; }
.bar .count { flex: 1; min-width: 0; font-size: 14px; line-height: 1.35; }
.bar .count b { font-size: 17px; }
.bar .count .saved { display: block; color: var(--muted); font-size: 12px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.bar button { padding: 8px 14px; }
.short { color: var(--warn); }
.readonly { white-space: pre-wrap; overflow-wrap: anywhere; font-family: Georgia, "Times New Roman", serif; line-height: 1.75; }

/* 反馈 */
.scores { display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; text-align: center; }
.scores > div { background: var(--bg); border-radius: 8px; padding: 6px 2px; }
.scores .k { font-size: 12px; color: var(--muted); line-height: 1.3; }
.scores .v { font-size: 20px; font-weight: 700; }
.scores .all { background: var(--accent); color: #fff; }
.scores .all .k { color: rgba(255,255,255,.85); }
.reasons p { margin: 8px 0 0; font-size: 15px; }
.reasons b { color: var(--accent); margin-right: 4px; }
mark {
  background: var(--mark); color: inherit; border-radius: 3px; padding: 0 1px; cursor: pointer;
  -webkit-box-decoration-break: clone; box-decoration-break: clone;
}
mark.on { background: var(--mark-on); }
mark sup { font-family: -apple-system, sans-serif; font-size: 11px; font-weight: 700; color: var(--bad); margin-left: 1px; }
.ann { border-left: 3px solid var(--line); padding: 4px 0 4px 12px; margin: 0 0 14px; scroll-margin-top: 70px; }
.ann.on { border-left-color: var(--mark-on); }
.ann .h { font-weight: 600; }
.ann .h .num { display: inline-block; min-width: 1.6em; color: var(--bad); }
.ann .code { font-weight: 400; font-size: 13px; color: var(--muted); margin-left: 6px; }
.ann .q { margin: 4px 0 0; overflow-wrap: anywhere; font-family: Georgia, "Times New Roman", serif; }
.ann .q s { color: var(--bad); text-decoration-thickness: 1px; }
.ann .q .fix { color: var(--accent); }
.ann .c { margin: 4px 0 0; font-size: 15px; }
ul.plain { margin: 0; padding-left: 1.2em; }
ul.plain li { margin: 4px 0; }
.kp b { margin-right: 6px; }
.history { font-size: 14px; }

#toast {
  position: fixed; left: 50%; bottom: 90px; transform: translateX(-50%); z-index: 20;
  background: rgba(0,0,0,.82); color: #fff; padding: 8px 16px; border-radius: 8px; font-size: 15px;
  opacity: 0; pointer-events: none; transition: opacity .2s; max-width: calc(100% - 32px);
}
#toast.show { opacity: 1; }

@media (min-width: 1100px) {
  main.wide { max-width: 1240px; }
  .work { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.15fr); gap: 20px; align-items: start; }
  .work .side .prompt-card { position: sticky; top: 64px; max-height: calc(100vh - 150px); overflow: auto; margin: 0; }
  .work textarea.essay { min-height: calc(100vh - 260px); }
}
@media (min-width: 720px) {
  main { padding-top: 24px; }
  h1 { font-size: 24px; }
  .scores .v { font-size: 24px; }
}