/* Летний курс математики — mobile-first.
   Базовая ширина: 360 px. Шрифт не меньше 16 px на input (чтобы Android/iOS не зумил).
   Touch target минимум 44×44 px. */

:root {
  --c-bg: #f6f7fb;
  --c-surface: #ffffff;
  --c-text: #1a2238;
  --c-muted: #6b7280;
  --c-border: #e3e6ef;
  --c-primary: #1f3864;
  --c-primary-2: #2c4f8f;
  --c-accent: #11873f;
  --c-warn: #b76b00;
  --c-error: #c0392b;
  --c-chip: #eef1f8;
  --c-chip-hover: #dde3f1;
  --r-md: 12px;
  --r-lg: 16px;
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-5: 24px;
  --sp-6: 32px;
  --shadow-1: 0 1px 3px rgba(20, 30, 60, 0.06), 0 2px 8px rgba(20, 30, 60, 0.04);
  --shadow-2: 0 4px 16px rgba(20, 30, 60, 0.12);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, "Noto Sans", "Apple Color Emoji", "Segoe UI Emoji";
}

* { box-sizing: border-box; }

html, body {
  margin: 0; padding: 0;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.5;
  -webkit-text-size-adjust: 100%;
}

body { min-height: 100vh; }

button, input, textarea, select {
  font: inherit;
  color: inherit;
}

input, textarea {
  font-size: 16px; /* против авто-зума */
}

.btn-primary {
  display: inline-flex; align-items: center; justify-content: center;
  background: var(--c-primary);
  color: #fff;
  border: 0;
  border-radius: var(--r-md);
  padding: 12px 18px;
  min-height: 44px;
  font-weight: 600;
  cursor: pointer;
}
.btn-primary:active { background: var(--c-primary-2); }
.btn-primary:disabled { opacity: .5; cursor: not-allowed; }

.btn-ghost {
  display: inline-flex; align-items: center; justify-content: center;
  background: transparent;
  color: var(--c-primary);
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  padding: 10px 14px;
  min-height: 44px;
  cursor: pointer;
}

/* ───── Login ───── */
.login-page {
  display: flex; align-items: center; justify-content: center;
  min-height: 100vh;
  padding: var(--sp-4);
  background: linear-gradient(180deg, #eaf0fb 0%, #f6f7fb 70%);
}
.login-card {
  background: var(--c-surface);
  border-radius: var(--r-lg);
  padding: var(--sp-5) var(--sp-4);
  box-shadow: var(--shadow-1);
  width: 100%; max-width: 360px;
}
.login-title { font-size: 22px; margin: 0 0 4px; color: var(--c-primary); }
.login-sub   { margin: 0 0 var(--sp-4); color: var(--c-muted); }
.login-form .field {
  display: block; margin-bottom: var(--sp-3);
}
.login-form .field span { display: block; font-size: 14px; color: var(--c-muted); margin-bottom: 4px; }
.login-form input {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  background: #fbfcfe;
}
.login-form .btn-primary { width: 100%; margin-top: var(--sp-3); }
.error { color: var(--c-error); margin: var(--sp-2) 0; font-size: 14px; }

/* ───── App shell ───── */
.loader { padding: 32px; text-align: center; color: var(--c-muted); }

.topbar {
  position: sticky; top: 0; z-index: 30;
  background: var(--c-primary);
  color: #fff;
  padding: 10px var(--sp-4);
  display: flex; align-items: center; gap: var(--sp-3);
  box-shadow: var(--shadow-1);
}
.topbar .back {
  background: transparent; border: 0; color: #fff;
  font-size: 22px; padding: 8px 4px; cursor: pointer; line-height: 1;
}
.topbar .crumbs { flex: 1; min-width: 0; }
.topbar .crumbs .t { font-weight: 600; font-size: 15px; line-height: 1.25; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; word-break: break-word; }
.topbar .crumbs .s { font-size: 12px; opacity: .85; }
.topbar .progress-bar { background: rgba(255,255,255,.2); border-radius: 4px; height: 6px; flex: 1; max-width: 120px; overflow: hidden; }
.topbar .progress-bar > div { background: #fff; height: 100%; transition: width .3s; }

.bottom-nav {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 25;
  background: var(--c-surface);
  border-top: 1px solid var(--c-border);
  display: flex; justify-content: space-around;
  padding: 6px 0 calc(6px + env(safe-area-inset-bottom));
}
.bottom-nav a {
  color: var(--c-muted);
  text-decoration: none;
  font-size: 12px;
  text-align: center;
  flex: 1; padding: 8px 4px;
  min-height: 44px;
  display: flex; flex-direction: column; align-items: center; gap: 2px;
}
.bottom-nav a.active { color: var(--c-primary); font-weight: 600; }
.bottom-nav a .ico { font-size: 20px; line-height: 1; }

main.page {
  padding: var(--sp-4);
  padding-bottom: calc(150px + env(safe-area-inset-bottom));
  max-width: 720px;
  margin: 0 auto;
}
/* Страница урока — sticky-чат выше → нужен больший отступ снизу */
main.page.has-chat {
  padding-bottom: calc(190px + env(safe-area-inset-bottom));
}

/* ───── Карта курса ───── */
.course-head {
  display: flex; align-items: baseline; justify-content: space-between;
  margin-bottom: var(--sp-3);
}
.course-head h1 { font-size: 20px; margin: 0; color: var(--c-primary); }
.course-head .meta { font-size: 13px; color: var(--c-muted); }

.week-label {
  font-size: 12px; text-transform: uppercase; letter-spacing: .04em;
  color: var(--c-muted); margin: var(--sp-4) 0 var(--sp-2);
}

.lesson-card {
  display: block;
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  padding: var(--sp-3) var(--sp-4);
  margin-bottom: var(--sp-2);
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow-1);
}
.lesson-card[data-status="locked"] {
  opacity: .55;
  pointer-events: none;
}
.lesson-card .row {
  display: flex; align-items: center; gap: var(--sp-3);
}
.lesson-card .status {
  width: 28px; height: 28px; flex: none;
  border-radius: 50%;
  display: inline-flex; align-items: center; justify-content: center;
  background: var(--c-chip);
  font-size: 15px;
}
.lesson-card[data-status="completed"] .status,
.lesson-card[data-status="replay"] .status { background: #e3f5ec; color: var(--c-accent); }
.lesson-card[data-status="in_progress"] .status { background: #fff5e0; color: var(--c-warn); }
.lesson-card[data-status="locked"] .status { background: #ecedf2; color: var(--c-muted); }
.lesson-card .title { font-weight: 600; }
.lesson-card .sub { font-size: 13px; color: var(--c-muted); margin-top: 2px; }
.lesson-card .cta {
  font-size: 13px; color: var(--c-primary); font-weight: 600;
  margin-top: var(--sp-2);
}

/* ───── Урок ───── */
.section {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-lg);
  padding: var(--sp-4);
  margin-bottom: var(--sp-4);
  box-shadow: var(--shadow-1);
}
.section h2 {
  font-size: 17px; margin: 0 0 var(--sp-2); color: var(--c-primary);
}
.section h3 {
  font-size: 15px; margin: var(--sp-3) 0 var(--sp-2);
}
.section p { margin: var(--sp-2) 0; }
.section .kicker { font-size: 12px; text-transform: uppercase; letter-spacing: .04em; color: var(--c-muted); margin-bottom: 4px; }

.callout {
  background: #eef4ff;
  border-left: 3px solid var(--c-primary);
  border-radius: 8px;
  padding: var(--sp-3);
  margin: var(--sp-3) 0;
  font-size: 15px;
}
.callout.warn { background: #fff5e0; border-color: var(--c-warn); }
.callout.ok   { background: #e3f5ec; border-color: var(--c-accent); }

/* Definition card — формальное определение */
.definition {
  border: 1px solid var(--c-primary);
  border-radius: 10px;
  padding: var(--sp-3);
  margin: var(--sp-3) 0;
  background: #fafbff;
}
.definition .def-term {
  font-weight: 700;
  color: var(--c-primary);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: .04em;
  margin-bottom: 6px;
}
.definition .def-body { font-size: 15px; line-height: 1.5; }
.definition .def-body p:first-child { margin-top: 0; }
.definition .def-body p:last-child { margin-bottom: 0; }

/* Collapse — сворачиваемый блок */
.collapse {
  border: 1px solid #e4e7ef;
  border-radius: 10px;
  margin: var(--sp-3) 0;
  background: #fff;
  overflow: hidden;
}
.collapse > summary {
  list-style: none;
  cursor: pointer;
  padding: var(--sp-3);
  font-weight: 600;
  color: var(--c-primary);
  font-size: 15px;
  display: flex;
  align-items: center;
  gap: 8px;
  user-select: none;
}
.collapse > summary::-webkit-details-marker { display: none; }
.collapse > summary::before {
  content: "▸";
  display: inline-block;
  transition: transform .15s ease;
  color: var(--c-muted);
  font-size: 12px;
}
.collapse[open] > summary::before { transform: rotate(90deg); }
.collapse > .collapse-body {
  padding: 0 var(--sp-3) var(--sp-3);
  font-size: 15px;
  line-height: 1.55;
  color: var(--c-text);
}
.collapse > .collapse-body p:first-child { margin-top: 0; }
.collapse > .collapse-body p:last-child  { margin-bottom: 0; }

.numline-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: var(--sp-3) calc(-1 * var(--sp-4));
  padding: 0 var(--sp-4);
}
.numline { width: 100%; min-width: 320px; }

/* Задачи */
.task {
  background: #fafbff;
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  padding: var(--sp-3);
  margin: var(--sp-3) 0;
}
.task .q { font-weight: 600; margin-bottom: var(--sp-2); }
.task .answer-row {
  display: flex; gap: var(--sp-2); align-items: stretch;
  margin-top: var(--sp-2);
}
.task input[type="text"], .task input[type="number"] {
  flex: 1;
  padding: 12px 14px;
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  background: #fff;
  min-width: 0;
}
.task input.correct { border-color: var(--c-accent); background: #f0faf4; }
.task input.wrong   { border-color: var(--c-error); background: #fdf2f0; }
.task .check-btn {
  background: var(--c-primary); color: #fff; border: 0;
  border-radius: var(--r-md);
  padding: 0 16px;
  min-height: 44px; min-width: 88px;
  font-weight: 600; cursor: pointer;
}
.task .options {
  display: flex; flex-direction: column; gap: 8px;
  margin: var(--sp-2) 0;
}
.task .option {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 14px;
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  background: #fff;
  cursor: pointer;
  min-height: 44px;
}
.task .option.selected { border-color: var(--c-primary); background: #eef4ff; }
.task .option.correct  { border-color: var(--c-accent); background: #f0faf4; }
.task .option.wrong    { border-color: var(--c-error); background: #fdf2f0; }
.task .option input { margin: 0; }

.task .feedback {
  margin-top: var(--sp-2);
  font-size: 14px;
}
.task .feedback.ok   { color: var(--c-accent); }
.task .feedback.fail { color: var(--c-error); }
.task .hint {
  margin-top: var(--sp-2);
  background: #fff5e0;
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 14px;
  color: var(--c-warn);
}
.task .solution {
  margin-top: var(--sp-2);
  background: #eef4ff;
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 14px;
}
.task .actions-row {
  display: flex; flex-wrap: wrap; gap: 8px;
  margin-top: var(--sp-2);
}
.task .save-wrong {
  background: transparent; border: 1px dashed var(--c-warn); color: var(--c-warn);
  border-radius: var(--r-md);
  padding: 8px 12px; font-size: 13px; cursor: pointer;
  min-height: 44px;
}
.task .open-chat {
  background: var(--c-chip); border: 0; color: var(--c-primary);
  border-radius: var(--r-md);
  padding: 8px 12px; font-size: 13px; cursor: pointer;
  min-height: 44px;
}
.task.discuss .open-chat { background: var(--c-primary); color: #fff; font-weight: 600; }

.section-nav {
  display: flex; justify-content: space-between; gap: var(--sp-2);
  margin-top: var(--sp-3);
}
.section-nav .btn-primary { flex: 1; }

.complete-form .opt {
  display: flex; gap: 8px;
}
.complete-form .opt label {
  flex: 1; padding: 12px; border: 1px solid var(--c-border); border-radius: var(--r-md);
  cursor: pointer; text-align: center; background: #fff; min-height: 44px;
  display: flex; align-items: center; justify-content: center;
}
.complete-form .opt input { display: none; }
.complete-form .opt input:checked + span { font-weight: 700; color: var(--c-primary); }
.complete-form .opt label:has(input:checked) { border-color: var(--c-primary); background: #eef4ff; }
.complete-form textarea {
  width: 100%; padding: 12px; border: 1px solid var(--c-border);
  border-radius: var(--r-md); min-height: 80px; margin-top: var(--sp-2);
  background: #fff; resize: vertical;
}

/* ───── Sticky-чат ───── */
.chat-fab {
  position: fixed; left: 0; right: 0; bottom: calc(56px + env(safe-area-inset-bottom));
  background: var(--c-surface);
  border-top: 1px solid var(--c-border);
  padding: 8px var(--sp-3);
  z-index: 28;
  box-shadow: 0 -2px 8px rgba(20,30,60,.06);
}
.chat-fab .row { display: flex; align-items: center; gap: 8px; }
.chat-fab .label { font-weight: 600; color: var(--c-primary); font-size: 14px; }
.chat-fab .open-btn {
  margin-left: auto;
  background: var(--c-primary); color: #fff; border: 0;
  border-radius: 999px; padding: 8px 14px; min-height: 36px;
  font-size: 13px; font-weight: 600; cursor: pointer;
}
.chat-fab .chips {
  display: flex; gap: 6px; overflow-x: auto;
  margin-top: 6px;
  -webkit-overflow-scrolling: touch;
  padding-bottom: 4px;
  padding-right: 24px;
  scroll-padding-right: 24px;
  mask-image: linear-gradient(to right, #000 calc(100% - 28px), transparent);
  -webkit-mask-image: linear-gradient(to right, #000 calc(100% - 28px), transparent);
}
.chat-fab .chips::-webkit-scrollbar { display: none; }
.chip {
  flex: none;
  background: var(--c-chip); color: var(--c-primary);
  border: 0; border-radius: 999px;
  padding: 8px 12px;
  font-size: 13px; cursor: pointer; white-space: nowrap;
  min-height: 36px;
}
.chip:active { background: var(--c-chip-hover); }

/* Раскрытое окно чата */
.chat-sheet {
  position: fixed; left: 0; right: 0; bottom: 0; top: 0;
  z-index: 50;
  background: rgba(20,30,60,.4);
  display: none;
}
.chat-sheet.open { display: flex; align-items: flex-end; }
.chat-sheet .panel {
  background: var(--c-surface);
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  border-top-left-radius: 18px;
  border-top-right-radius: 18px;
  height: 80vh;
  display: flex; flex-direction: column;
  padding-bottom: env(safe-area-inset-bottom);
}
.chat-sheet header {
  display: flex; align-items: center; gap: 8px;
  padding: var(--sp-3) var(--sp-4);
  border-bottom: 1px solid var(--c-border);
}
.chat-sheet header .title { font-weight: 600; color: var(--c-primary); flex: 1; }
.chat-sheet header .close {
  background: var(--c-chip); border: 0;
  border-radius: 50%; width: 36px; height: 36px;
  font-size: 18px; cursor: pointer;
}

.chat-log {
  flex: 1; overflow-y: auto;
  padding: var(--sp-3) var(--sp-4);
  display: flex; flex-direction: column; gap: 10px;
}
.chat-msg {
  max-width: 85%;
  padding: 10px 12px;
  border-radius: 14px;
  font-size: 15px;
  white-space: pre-wrap;
  word-wrap: break-word;
}
.chat-msg.user { align-self: flex-end; background: var(--c-primary); color: #fff; border-bottom-right-radius: 4px; }
.chat-msg.assistant { align-self: flex-start; background: var(--c-chip); color: var(--c-text); border-bottom-left-radius: 4px; }
.chat-msg.system { align-self: center; background: #fff5e0; color: var(--c-warn); font-size: 13px; }

.chat-input-row {
  display: flex; gap: 8px;
  padding: var(--sp-3) var(--sp-4);
  border-top: 1px solid var(--c-border);
}
.chat-input-row textarea {
  flex: 1; resize: none;
  border: 1px solid var(--c-border); border-radius: var(--r-md);
  padding: 10px 12px;
  font-size: 16px;
  max-height: 120px; min-height: 44px;
  background: #fbfcfe;
}
.chat-input-row .send {
  background: var(--c-primary); color: #fff; border: 0;
  border-radius: 50%; width: 44px; height: 44px;
  font-size: 18px; cursor: pointer; flex: none;
}
.chat-input-row .send:disabled { opacity: .5; }

.chat-sheet .chips-row {
  display: flex; gap: 6px; overflow-x: auto;
  padding: 8px var(--sp-4) 0;
  -webkit-overflow-scrolling: touch;
}
.chat-sheet .chips-row::-webkit-scrollbar { display: none; }

/* ───── Дневник ───── */
.tabs {
  display: flex; gap: 4px;
  background: var(--c-chip);
  border-radius: var(--r-md);
  padding: 4px;
  margin-bottom: var(--sp-3);
}
.tabs button {
  flex: 1; background: transparent; border: 0; padding: 10px;
  border-radius: 8px; cursor: pointer; min-height: 44px;
  font-weight: 600; color: var(--c-muted);
}
.tabs button.active { background: var(--c-surface); color: var(--c-primary); box-shadow: var(--shadow-1); }

.diary-row {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--r-md);
  padding: var(--sp-3);
  margin-bottom: var(--sp-2);
  display: flex; gap: var(--sp-3); align-items: flex-start;
}
.diary-row .lbl-asses {
  flex: none;
  font-size: 12px; padding: 4px 8px; border-radius: 999px;
}
.lbl-asses.clear { background: #e3f5ec; color: var(--c-accent); }
.lbl-asses.shaky { background: #fff5e0; color: var(--c-warn); }
.lbl-asses.unclear { background: #fdecea; color: var(--c-error); }
.lbl-asses.none { background: var(--c-chip); color: var(--c-muted); }

/* Tablet+ */
@media (min-width: 600px) {
  main.page { padding: var(--sp-5) var(--sp-5); padding-bottom: calc(160px + env(safe-area-inset-bottom)); }
  main.page.has-chat { padding-bottom: calc(200px + env(safe-area-inset-bottom)); }
  .course-head h1 { font-size: 24px; }
  .section { padding: var(--sp-5); }
  .section h2 { font-size: 19px; }
}

@media (min-width: 900px) {
  .chat-sheet .panel { max-width: 720px; border-radius: 18px; height: 70vh; margin-bottom: 5vh; }
  .chat-sheet.open { align-items: center; }
}