:root {
  --bg: #f7f7f5; --panel: #ffffff; --text: #1d1f23; --muted: #666b75; --line: #dcdfe4;
  --accent: #1f5fbf; --accent-text: #ffffff;
  --good-bg: #e8f5ec; --good-line: #3c9a5f; --warn-bg: #fdf3e0; --warn-line: #c9892b;
  --note-bg: #eaf1fb; --note-line: #6b95d6;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15171a; --panel: #1e2126; --text: #e6e8eb; --muted: #9aa1ac; --line: #343942;
    --accent: #6ea4f4; --accent-text: #10141a;
    --good-bg: #1b2e23; --good-line: #4fae74; --warn-bg: #33291a; --warn-line: #d09a45;
    --note-bg: #1c2636; --note-line: #5f86c4;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
header {
  display: flex; flex-wrap: wrap; gap: 8px 20px; align-items: center; justify-content: space-between;
  padding: 12px 16px; border-bottom: 1px solid var(--line); background: var(--panel);
}
header .brand { font-weight: 700; color: var(--text); text-decoration: none; }
nav { display: flex; flex-wrap: wrap; gap: 4px 16px; }
main { max-width: 760px; margin: 0 auto; padding: 16px 16px 64px; }
a { color: var(--accent); }
h1 { font-size: 1.6rem; line-height: 1.25; margin: 0.4em 0; }
h2 { font-size: 1.2rem; margin: 1.6em 0 0.4em; }
h3 { font-size: 1rem; margin: 1.2em 0 0.3em; }
.muted { color: var(--muted); font-size: 0.92rem; }
.card, .question {
  background: var(--panel); border: 1px solid var(--line); border-radius: 10px;
  padding: 16px; margin: 16px 0;
}
.card h2 { margin-top: 0; }
.button, button {
  display: inline-block; background: var(--accent); color: var(--accent-text); border: 0;
  border-radius: 8px; padding: 10px 18px; font: inherit; font-weight: 600; text-decoration: none; cursor: pointer;
}
button:disabled { opacity: 0.6; cursor: wait; }
button.secondary { background: transparent; color: var(--accent); border: 1px solid var(--accent); padding: 6px 12px; font-weight: 500; }
textarea, input[type="text"] {
  width: 100%; margin: 8px 0; padding: 10px; font: inherit; color: var(--text);
  background: var(--bg); border: 1px solid var(--line); border-radius: 8px;
}
label.file { display: block; margin: 8px 0; }
.box { border-left: 4px solid var(--note-line); background: var(--note-bg); border-radius: 6px; padding: 10px 14px; margin: 12px 0; }
.box.correct { border-color: var(--good-line); background: var(--good-bg); }
.box.revise { border-color: var(--warn-line); background: var(--warn-bg); }
.box p { margin: 4px 0; }
.label { font-size: 0.85rem; font-weight: 700; color: var(--muted); }
.answer { white-space: pre-wrap; font-style: italic; }
.prompt p { display: inline; }
.photo { max-width: 100%; max-height: 360px; border-radius: 6px; display: block; margin: 8px 0; }
.lesson-body figure { margin: 0; }
.lesson-body svg { max-width: 100%; height: auto; display: block; margin: 12px auto; }
.lesson-body blockquote { margin: 12px 0; padding: 4px 14px; border-left: 4px solid var(--note-line); background: var(--note-bg); border-radius: 6px; }
.scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 0.92rem; }
th, td { text-align: left; padding: 6px 10px; border-bottom: 1px solid var(--line); vertical-align: top; }
dl { margin: 8px 0; }
dt { font-weight: 700; margin-top: 8px; }
dd { margin: 0 0 0 0; color: var(--text); }
ul.lessons { list-style: none; padding: 0; margin: 0; }
ul.lessons li { padding: 4px 0; }
.tick { display: inline-block; width: 1.4em; color: var(--good-line); font-weight: 700; }
fieldset.likert { border: 0; padding: 0; margin: 14px 0; }
fieldset.likert legend { font-weight: 600; padding: 0; }
.scale { display: flex; gap: 8px; margin: 8px 0 4px; }
.scale label { flex: 1; text-align: center; }
.scale input { position: absolute; opacity: 0; }
.scale span { display: block; padding: 8px 0; border: 1px solid var(--line); border-radius: 8px; cursor: pointer; }
.scale input:checked + span { background: var(--accent); color: var(--accent-text); border-color: var(--accent); }
.scale input:focus-visible + span { outline: 2px solid var(--accent); outline-offset: 2px; }
.ends { display: flex; justify-content: space-between; gap: 8px; font-size: 0.8rem; color: var(--muted); }