/* ==========================================================================
   Web Development course — design tokens
   ========================================================================== */
:root {
  --bg:            #0b1020;
  --bg-panel:      #111827;
  --bg-elev:       #161f36;
  --bg-input:      #0e1526;
  --border:        #243049;
  --border-soft:   #1b2439;
  --text:          #e5e9f5;
  --text-dim:      #9aa6c4;
  --text-faint:    #6b7796;
  --accent:        #6ea8fe;
  --accent-strong: #3b82f6;
  --ok:            #34d399;
  --ok-bg:         #0d2a22;
  --warn:          #fbbf24;
  --err:           #f87171;
  --err-bg:        #2a1114;
  --easy:          #34d399;
  --medium:        #fbbf24;
  --hard:          #f87171;
  --radius:        10px;
  --radius-sm:     6px;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --shadow: 0 10px 30px rgb(0 0 0 / .35);
}
:root[data-theme="light"] {
  --bg:            #f4f6fb;
  --bg-panel:      #ffffff;
  --bg-elev:       #f7f9ff;
  --bg-input:      #fbfcff;
  --border:        #d7deee;
  --border-soft:   #e6ebf6;
  --text:          #16203a;
  --text-dim:      #55618a;
  --text-faint:    #7a85a8;
  --accent:        #2563eb;
  --accent-strong: #1d4ed8;
  --ok:            #0f9d68;
  --ok-bg:         #e7f7f0;
  --err:           #d64545;
  --err-bg:        #fdecec;
  --easy:          #0f9d68;
  --medium:        #b7791f;
  --hard:          #d64545;
  --shadow: 0 8px 24px rgb(20 30 60 / .10);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}
button, input, select, textarea { font: inherit; color: inherit; }
a { color: var(--accent); }

.boot { padding: 40px; color: var(--text-dim); }

/* ==========================================================================
   App layout
   ========================================================================== */
.app {
  height: 100%;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
}

/* ---- header ---- */
.top {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 10px 16px;
  background: var(--bg-panel);
  border-bottom: 1px solid var(--border);
  min-height: 56px;
}
.top__burger {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 7px 10px;
  cursor: pointer;
  line-height: 1;
}
.top__burger:hover { border-color: var(--accent); }
.top__title { display: flex; flex-direction: column; min-width: 0; }
.top__lesson {
  font-weight: 650;
  font-size: 15px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.top__module { font-size: 12px; color: var(--text-faint); }
.top__spacer { flex: 1 1 auto; }
.top__counter {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-dim);
  padding: 4px 8px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
  white-space: nowrap;
}
.top__nav { display: flex; gap: 6px; }

/* ---- generic buttons ---- */
.btn {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: var(--radius-sm);
  padding: 7px 12px;
  cursor: pointer;
  white-space: nowrap;
  transition: border-color .12s, background .12s, opacity .12s;
}
.btn:hover:not(:disabled) { border-color: var(--accent); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn--primary { background: var(--accent-strong); border-color: var(--accent-strong); color: #fff; font-weight: 600; }
.btn--primary:hover:not(:disabled) { filter: brightness(1.08); }
.btn--ok { background: var(--ok); border-color: var(--ok); color: #05261b; font-weight: 600; }
.btn--ok:hover:not(:disabled) { filter: brightness(1.06); }
.btn--sm { padding: 4px 9px; font-size: 13px; }
.btn--ghost { background: transparent; }

/* ---- main grid: theory | playground | tasks ---- */
.main {
  display: grid;
  grid-template-columns: minmax(240px, 22%) minmax(0, 1fr) minmax(260px, 23%);
  min-height: 0;
}
.main--no-theory { grid-template-columns: minmax(0, 1fr) minmax(260px, 23%); }

/* ---- theory ---- */
.theory {
  overflow: auto;
  padding: 18px 20px 40px;
  border-right: 1px solid var(--border);
  background: var(--bg-panel);
}
.theory h2 { font-size: 19px; margin: 0 0 4px; }
.theory h3 { font-size: 15px; margin: 22px 0 6px; color: var(--text); }
.theory p { margin: 0 0 10px; color: var(--text-dim); }
.theory ul, .theory ol { margin: 0 0 12px; padding-left: 20px; color: var(--text-dim); }
.theory li { margin-bottom: 4px; }
.theory code {
  font-family: var(--mono);
  font-size: .88em;
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  border-radius: 4px;
  padding: 1px 5px;
  color: var(--text);
  word-break: break-word;
}
.theory pre {
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.5;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  overflow: auto;
  margin: 0 0 12px;
}
.theory pre code { background: none; border: 0; padding: 0; }
.theory__lead { color: var(--text); font-size: 14.5px; margin-bottom: 14px; }
.note {
  border-left: 3px solid var(--accent);
  background: var(--bg-elev);
  padding: 9px 12px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 0 0 12px;
  color: var(--text-dim);
  font-size: 14px;
}
.note--warn { border-left-color: var(--warn); }
.table-wrap { overflow-x: auto; margin: 0 0 12px; }
.theory table { border-collapse: collapse; width: 100%; font-size: 13.5px; }
.theory th, .theory td {
  border: 1px solid var(--border);
  padding: 6px 9px;
  text-align: left;
  color: var(--text-dim);
}
.theory th { background: var(--bg-elev); color: var(--text); font-weight: 600; }

/* ---- playground ---- */
.pg { display: grid; grid-template-rows: auto minmax(0, 1fr); min-width: 0; min-height: 0; }
.pg__bar {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-panel);
  flex-wrap: wrap;
}
.tabs { display: flex; gap: 4px; }
.tab {
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  padding: 5px 12px;
  cursor: pointer;
  color: var(--text-dim);
  font-size: 13px;
  font-family: var(--mono);
  text-transform: uppercase;
  letter-spacing: .04em;
}
.tab:hover { color: var(--text); }
.tab[aria-selected="true"] {
  background: var(--bg-elev);
  border-color: var(--border);
  color: var(--text);
  font-weight: 600;
}
.tab[disabled] { opacity: .35; cursor: not-allowed; }
.tab__dot { color: var(--accent); }
.pg__actions { display: flex; gap: 6px; margin-left: auto; }

.pg__split {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  min-height: 0;
}
.pg__split--stack { grid-template-columns: minmax(0, 1fr); grid-template-rows: minmax(0, 1fr) minmax(0, 1fr); }

/* ---- editor ---- */
.editor {
  position: relative;
  display: grid;
  grid-template-rows: minmax(0, 1fr) auto;
  border-right: 1px solid var(--border);
  min-width: 0;
  background: var(--bg-input);
}
.editor__pane { position: relative; display: flex; min-height: 0; overflow: hidden; }
.editor__gutter {
  flex: 0 0 auto;
  padding: 10px 6px 10px 10px;
  text-align: right;
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.55;
  color: var(--text-faint);
  background: var(--bg-input);
  border-right: 1px solid var(--border-soft);
  user-select: none;
  overflow: hidden;
  white-space: pre;
}
.editor__area {
  flex: 1 1 auto;
  border: 0;
  outline: none;
  resize: none;
  background: transparent;
  color: var(--text);
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.55;
  padding: 10px 12px;
  tab-size: 2;
  white-space: pre;
  overflow: auto;
}
.editor__area::placeholder { color: var(--text-faint); }
.editor__hintbar {
  border-top: 1px solid var(--border-soft);
  padding: 4px 10px;
  font-size: 11.5px;
  color: var(--text-faint);
  font-family: var(--mono);
  display: flex;
  gap: 12px;
}

/* ---- preview + console ---- */
.preview {
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) minmax(120px, 34%);
  min-width: 0;
  min-height: 0;
  background: var(--bg-panel);
}
.preview__label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--text-faint);
  padding: 6px 12px;
  border-bottom: 1px solid var(--border-soft);
  display: flex;
  align-items: center;
  gap: 8px;
}
.preview__frame { width: 100%; height: 100%; border: 0; background: #fff; display: block; }
.console {
  border-top: 1px solid var(--border);
  background: var(--bg-input);
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  min-height: 0;
}
.console__head {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 4px 10px;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--text-faint);
  border-bottom: 1px solid var(--border-soft);
}
.console__body {
  overflow: auto;
  min-height: 0;
  padding: 6px 10px;
  font-family: var(--mono);
  font-size: 12px;
  line-height: 1.5;
}
.console__line { white-space: pre-wrap; word-break: break-word; border-bottom: 1px solid var(--border-soft); padding: 2px 0; }
.console__line:last-child { border-bottom: 0; }
.console__line--error { color: var(--err); }
.console__line--warn { color: var(--warn); }
.console__line--alert { color: var(--accent); }
.console__line--info { color: var(--text-dim); }
.console__empty { color: var(--text-faint); font-style: italic; }

/* ==========================================================================
   Tasks dock
   ========================================================================== */
.tasks {
  border-left: 1px solid var(--border);
  background: var(--bg-panel);
  display: grid;
  grid-template-rows: auto auto minmax(0, 1fr);
  min-height: 0;
  min-width: 0;
}
.tasks__head {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-soft);
  flex-wrap: wrap;
}
.tasks__progress { margin-left: auto; }
.tasks__title { font-size: 11px; text-transform: uppercase; letter-spacing: .1em; color: var(--text-faint); }
.tasks__progress { font-family: var(--mono); font-size: 12px; color: var(--text-dim); }
.tasks__list {
  display: flex;
  flex-direction: column;
  gap: 5px;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border-soft);
}
.task-chip {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
  text-align: left;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 7px 10px;
  cursor: pointer;
  font-size: 13px;
  color: var(--text-dim);
}
.task-chip__label { flex: 1 1 auto; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.task-chip:hover { border-color: var(--accent); color: var(--text); }
.task-chip[aria-current="true"] { border-color: var(--accent); background: var(--bg-input); color: var(--text); font-weight: 600; }
.task-chip__mark { font-family: var(--mono); font-size: 13px; color: var(--text-faint); }
.task-chip--done .task-chip__mark { color: var(--ok); }
.task-chip__dif { width: 8px; height: 8px; border-radius: 50%; flex: 0 0 auto; }
.dif--easy   { background: var(--easy); }
.dif--medium { background: var(--medium); }
.dif--hard   { background: var(--hard); }

.task-panel { padding: 12px 14px 20px; overflow: auto; min-height: 0; }
.task-panel__top { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
.task-panel h4 { margin: 0; font-size: 15px; }
.task-panel__desc { margin: 6px 0 8px; color: var(--text-dim); font-size: 13.5px; }
.task-panel__desc code {
  font-family: var(--mono);
  font-size: .9em;
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  border-radius: 4px;
  padding: 1px 5px;
}
.task-panel__tools { display: flex; gap: 6px; flex-wrap: wrap; margin-top: 4px; }
.badge {
  font-size: 11px;
  border-radius: 999px;
  padding: 2px 9px;
  border: 1px solid var(--border);
  color: var(--text-dim);
  white-space: nowrap;
}
.badge--easy   { color: var(--easy);   border-color: color-mix(in srgb, var(--easy) 45%, transparent); }
.badge--medium { color: var(--medium); border-color: color-mix(in srgb, var(--medium) 45%, transparent); }
.badge--hard   { color: var(--hard);   border-color: color-mix(in srgb, var(--hard) 45%, transparent); }
.badge--done   { color: var(--ok); border-color: color-mix(in srgb, var(--ok) 45%, transparent); }

.hints { margin: 8px 0 0; padding: 0; list-style: none; }
.hints li {
  border-left: 3px solid var(--warn);
  background: var(--bg-elev);
  padding: 7px 11px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin-bottom: 6px;
  font-size: 13.5px;
  color: var(--text-dim);
}

/* ---- check results ---- */
.results { margin: 10px 0 0; padding: 0; list-style: none; display: grid; gap: 4px; }
.results li {
  display: flex;
  gap: 8px;
  align-items: flex-start;
  flex-wrap: wrap;
  font-size: 13.5px;
  padding: 5px 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-soft);
  background: var(--bg-elev);
}
.results li.pass { color: var(--ok); }
.results li.fail { color: var(--err); }
.results__mark { font-family: var(--mono); flex: 0 0 auto; }
.results__msg { color: var(--text-faint); }
.banner {
  margin-top: 10px;
  padding: 9px 12px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 14px;
}
.banner--ok   { background: var(--ok-bg);  color: var(--ok);  border: 1px solid color-mix(in srgb, var(--ok) 35%, transparent); }
.banner--fail { background: var(--err-bg); color: var(--err); border: 1px solid color-mix(in srgb, var(--err) 35%, transparent); }

/* ==========================================================================
   Sidebar (course map)
   ========================================================================== */
.scrim {
  position: fixed;
  inset: 0;
  background: rgb(0 0 0 / .5);
  z-index: 20;
}
.scrim[hidden] { display: none; }
.sidebar {
  position: fixed;
  inset: 0 auto 0 0;
  width: min(360px, 88vw);
  background: var(--bg-panel);
  border-right: 1px solid var(--border);
  z-index: 21;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  box-shadow: var(--shadow);
}
.sidebar[hidden] { display: none; }
.sidebar__head { padding: 14px 16px; border-bottom: 1px solid var(--border); display: flex; align-items: center; gap: 10px; }
.sidebar__head h2 { margin: 0; font-size: 15px; }
.sidebar__body { overflow: auto; padding: 10px 10px 20px; }
.sidebar__foot { padding: 10px 14px; border-top: 1px solid var(--border); display: flex; gap: 8px; flex-wrap: wrap; }
.mod { margin-bottom: 16px; }
.mod__head { display: flex; align-items: baseline; gap: 8px; padding: 0 6px 4px; }
.mod__name { font-size: 12px; text-transform: uppercase; letter-spacing: .08em; color: var(--text-faint); }
.mod__stat { font-family: var(--mono); font-size: 11.5px; color: var(--text-faint); margin-left: auto; }
.bar { height: 6px; border-radius: 999px; background: var(--bg-input); border: 1px solid var(--border-soft); overflow: hidden; margin: 0 6px 8px; }
.bar__fill { height: 100%; background: var(--accent); border-radius: 999px; transition: width .25s; }
.bar__fill--done { background: var(--ok); }
.lessons { list-style: none; margin: 0; padding: 0; }
.lesson-item {
  display: flex;
  align-items: center;
  gap: 9px;
  width: 100%;
  text-align: left;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  padding: 6px 8px;
  cursor: pointer;
  color: var(--text-dim);
  font-size: 13.5px;
}
.lesson-item:hover { background: var(--bg-elev); color: var(--text); }
.lesson-item[aria-current="true"] { border-color: var(--accent); background: var(--bg-elev); color: var(--text); }
.lesson-item__num { font-family: var(--mono); font-size: 12px; color: var(--text-faint); width: 22px; flex: 0 0 auto; }
.lesson-item__name { flex: 1 1 auto; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.lesson-item__tasks { font-family: var(--mono); font-size: 11.5px; color: var(--text-faint); }
.lesson-item--done .lesson-item__tasks { color: var(--ok); }

/* ==========================================================================
   Toast
   ========================================================================== */
.toasts { position: fixed; right: 16px; bottom: 16px; display: grid; gap: 8px; z-index: 40; }
.toast {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 9px 14px;
  box-shadow: var(--shadow);
  font-size: 14px;
  max-width: 340px;
  animation: toast-in .18s ease-out;
}
.toast--ok { border-left-color: var(--ok); }
.toast--err { border-left-color: var(--err); }
@keyframes toast-in { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }

@media (prefers-reduced-motion: reduce) {
  * { animation-duration: .001ms !important; transition-duration: .001ms !important; }
}

/* ==========================================================================
   Responsive
   ========================================================================== */
@media (max-width: 1280px) {
  /* Tasks drop under the playground, keeping the editor usable. */
  .main {
    grid-template-columns: minmax(220px, 26%) minmax(0, 1fr);
    grid-template-rows: minmax(0, 1fr) minmax(200px, 38%);
  }
  .main--no-theory { grid-template-columns: minmax(0, 1fr); }
  .theory { grid-row: span 2; }
  .tasks {
    border-left: 0;
    border-top: 1px solid var(--border);
    grid-template-rows: auto auto minmax(0, 1fr);
  }
  .tasks__list { flex-direction: row; overflow-x: auto; }
  .task-chip { width: auto; white-space: nowrap; }
  .task-chip__label { white-space: nowrap; }
}

@media (max-width: 1080px) {
  /* One column: the page scrolls instead of squeezing every region flat. */
  .app { height: auto; min-height: 100%; }
  .main {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto auto auto;
  }
  .theory {
    grid-row: auto;
    border-right: 0;
    border-bottom: 1px solid var(--border);
    max-height: 40vh;
  }
  .pg { min-height: 78vh; }
  .pg__split {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: minmax(220px, 1fr) minmax(320px, 1fr);
  }
  .editor { border-right: 0; border-bottom: 1px solid var(--border); }
  .preview { grid-template-rows: auto minmax(180px, 1fr) minmax(120px, 32%); }
  .tasks { min-height: 60vh; }
}

@media (max-width: 720px) {
  body { font-size: 14px; }
  .theory { max-height: none; }
  .pg__split { grid-template-rows: minmax(260px, auto) minmax(360px, auto); }
  .preview { grid-template-rows: auto 240px minmax(140px, auto); }
  .top { flex-wrap: wrap; }
  .top__counter { order: 3; }
}