/* ==========================================================================
   App shell layout
   ========================================================================== */

.app {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
  grid-template-rows: var(--header-h) minmax(0, 1fr);
  grid-template-areas:
    "header header"
    "sidebar main";
  min-height: 100dvh;
}
.app[data-sidebar="closed"] { --sidebar-w: 0px; }

/* ---------- Header ---------- */
.app-header {
  grid-area: header;
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: 0 var(--sp-4);
  background: color-mix(in oklab, var(--bg-elev) 88%, transparent);
  backdrop-filter: blur(12px) saturate(140%);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  font-weight: var(--fw-bold);
  letter-spacing: -0.02em;
  color: var(--text);
  text-decoration: none;
  flex: none;
}
.brand__mark {
  display: grid;
  place-items: center;
  width: 30px; height: 30px;
  font: var(--fw-bold) 0.75rem/1 var(--font-mono);
  color: var(--accent-contrast);
  background: linear-gradient(135deg, var(--accent), #b58cff);
  border-radius: var(--r-sm);
}
.brand__text { font-size: var(--fs-md); }
@media (max-width: 560px) { .brand__text { display: none; } }

.breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  min-width: 0;
  font-size: var(--fs-sm);
  color: var(--text-faint);
}
.breadcrumb a { color: var(--text-dim); text-decoration: none; }
.breadcrumb a:hover { color: var(--text); }
.breadcrumb__sep { opacity: 0.5; }
.breadcrumb__current {
  color: var(--text);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
@media (max-width: 900px) { .breadcrumb { display: none; } }

/* ---------- Sidebar ---------- */
.sidebar {
  grid-area: sidebar;
  position: sticky;
  top: var(--header-h);
  align-self: start;
  height: calc(100dvh - var(--header-h));
  overflow: hidden auto;
  overscroll-behavior: contain;
  background: var(--bg-elev);
  border-right: 1px solid var(--border);
  scrollbar-width: thin;
}
.app[data-sidebar="closed"] .sidebar { display: none; }

.sidebar__section { padding: var(--sp-4) var(--sp-3); }
.sidebar__section + .sidebar__section { border-top: 1px solid var(--border); }
.sidebar__label {
  padding: 0 var(--sp-2) var(--sp-2);
  font-size: var(--fs-xs);
  font-weight: var(--fw-semi);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-faint);
}

@media (max-width: 1024px) {
  .app { grid-template-columns: minmax(0, 1fr); grid-template-areas: "header" "main"; }
  .sidebar {
    position: fixed;
    inset: var(--header-h) auto 0 0;
    z-index: var(--z-drawer);
    width: min(320px, 86vw);
    height: auto;
    box-shadow: var(--sh-4);
    transform: translateX(-102%);
    transition: transform var(--dur) var(--ease);
  }
  .app[data-sidebar="open"] .sidebar { display: block; transform: none; }
  .app[data-sidebar="closed"] .sidebar { display: block; }
  .scrim {
    position: fixed;
    inset: var(--header-h) 0 0;
    z-index: calc(var(--z-drawer) - 1);
    background: rgb(0 0 0 / 0.5);
    animation: fade-in var(--dur) var(--ease);
  }
}
@media (min-width: 1025px) { .scrim { display: none; } }

/* ---------- Main ---------- */
.main {
  grid-area: main;
  min-width: 0;
  padding: var(--sp-6) var(--sp-5) var(--sp-9);
}
@media (max-width: 640px) { .main { padding: var(--sp-4) var(--sp-3) var(--sp-8); } }

.view { max-width: var(--content-max); margin: 0 auto; animation: view-in var(--dur) var(--ease); }
@keyframes view-in { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
@keyframes fade-in { from { opacity: 0; } to { opacity: 1; } }

/* ---------- Generic grids ---------- */
.grid {
  display: grid;
  gap: var(--sp-4);
  grid-template-columns: repeat(auto-fill, minmax(min(280px, 100%), 1fr));
}
.grid--wide { grid-template-columns: repeat(auto-fill, minmax(min(340px, 100%), 1fr)); }
.grid--2 { grid-template-columns: repeat(auto-fit, minmax(min(320px, 100%), 1fr)); }

/* ---------- Split pane (editor | console) ---------- */
.split {
  display: grid;
  grid-template-columns: minmax(0, var(--split, 1fr)) 6px minmax(0, 1fr);
  align-items: stretch;
  min-height: 0;
}
.split__handle {
  cursor: col-resize;
  background: var(--border);
  border-radius: var(--r-full);
  transition: background var(--dur-fast) var(--ease);
}
.split__handle:hover, .split__handle:focus-visible { background: var(--accent); }
@media (max-width: 1080px) {
  .split { grid-template-columns: minmax(0, 1fr); grid-template-rows: auto auto; }
  .split__handle { display: none; }
}

/* ---------- Sticky lesson footer nav ---------- */
.lesson-nav {
  position: sticky;
  bottom: 0;
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  margin-top: var(--sp-7);
  padding: var(--sp-3) var(--sp-4);
  background: color-mix(in oklab, var(--bg-elev) 92%, transparent);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  box-shadow: var(--sh-2);
}
@media (max-width: 640px) {
  .lesson-nav { flex-wrap: wrap; }
  .lesson-nav .btn { flex: 1 1 auto; justify-content: center; }
}

/* ---------- Footer ----------
   Spans the full width under both columns, so it reads as the end of the site rather than
   the end of the article. Lives outside `main`, so swapping a view never removes it.
*/
.app {
  grid-template-areas:
    "header header"
    "sidebar main"
    "footer footer";
  grid-template-rows: var(--header-h) minmax(0, 1fr) auto;
}
@media (max-width: 1024px) {
  .app {
    grid-template-areas: "header" "main" "footer";
    grid-template-rows: var(--header-h) minmax(0, 1fr) auto;
  }
}

.app-footer {
  grid-area: footer;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-2) var(--sp-5);
  padding: var(--sp-5);
  font-size: var(--fs-xs);
  color: var(--text-faint);
  background: var(--bg-sunken);
  border-top: 1px solid var(--border);
}
.app-footer__row { display: flex; flex-wrap: wrap; align-items: center; gap: var(--sp-2) var(--sp-3); }
.app-footer__row strong { color: var(--text-dim); font-weight: var(--fw-semi); }
.app-footer__sep { opacity: 0.5; }
.app-footer__mark {
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  font: var(--fw-bold) 10px/1 var(--font-display);
  color: var(--accent-contrast);
  background: linear-gradient(135deg, var(--accent), #b58cff);
  border-radius: var(--r-xs);
}
.app-footer a { color: var(--text-dim); text-decoration: none; }
.app-footer a:hover { color: var(--accent); text-decoration: underline; }

/* Printing a lesson should not print the chrome. */
@media print {
  .app-header, .sidebar, .app-footer, .reward { display: none !important; }
  .app { grid-template-areas: "main"; grid-template-columns: 1fr; grid-template-rows: 1fr; }
}