/* LernBau — Apple-style UI with a playful touch. */

:root {
  color-scheme: light dark;
  --bg: #F2F2F7;
  --bg-elev: #FFFFFF;
  --bg-elev2: #F2F2F7;
  --fill: rgba(120, 120, 128, 0.16);
  --fill2: rgba(120, 120, 128, 0.08);
  --label: #000000;
  --label2: rgba(60, 60, 67, 0.62);
  --label3: rgba(60, 60, 67, 0.32);
  --sep: rgba(60, 60, 67, 0.16);
  --glass: rgba(255, 255, 255, 0.72);
  --glass-border: rgba(255, 255, 255, 0.6);
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.04), 0 8px 24px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.12);
  --accent: #007AFF;
  --accent-ink: #FFFFFF;
  --green: #34C759;
  --green-d: #248A3D;
  --red: #FF3B30;
  --red-d: #C9271E;
  --orange: #FF9500;
  --orange-d: #C46F00;
  --blue: #007AFF;
  --blue-d: #0058BC;
  --yellow: #FFCC00;
  --purple: #AF52DE;
  --flame: #FF6B00;
  --radius: 22px;
  --radius-sm: 14px;
  --tabbar-h: 64px;
  --safe-b: env(safe-area-inset-bottom, 0px);
  --safe-t: env(safe-area-inset-top, 0px);
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", "Helvetica Neue", system-ui, sans-serif;
  --font-round: ui-rounded, "SF Pro Rounded", -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #000000;
    --bg-elev: #1C1C1E;
    --bg-elev2: #2C2C2E;
    --fill: rgba(120, 120, 128, 0.36);
    --fill2: rgba(120, 120, 128, 0.2);
    --label: #FFFFFF;
    --label2: rgba(235, 235, 245, 0.62);
    --label3: rgba(235, 235, 245, 0.3);
    --sep: rgba(84, 84, 88, 0.6);
    --glass: rgba(30, 30, 32, 0.72);
    --glass-border: rgba(255, 255, 255, 0.08);
    --shadow: none;
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.6);
    --accent: #0A84FF;
    --green: #30D158;
    --green-d: #1E8E3E;
    --red: #FF453A;
    --red-d: #C2302A;
    --orange: #FF9F0A;
    --blue: #0A84FF;
    --blue-d: #0060C0;
  }
}
:root[data-theme="dark"] {
  --bg: #000000;
  --bg-elev: #1C1C1E;
  --bg-elev2: #2C2C2E;
  --fill: rgba(120, 120, 128, 0.36);
  --fill2: rgba(120, 120, 128, 0.2);
  --label: #FFFFFF;
  --label2: rgba(235, 235, 245, 0.62);
  --label3: rgba(235, 235, 245, 0.3);
  --sep: rgba(84, 84, 88, 0.6);
  --glass: rgba(30, 30, 32, 0.72);
  --glass-border: rgba(255, 255, 255, 0.08);
  --shadow: none;
  --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.6);
  --accent: #0A84FF;
  --green: #30D158;
  --green-d: #1E8E3E;
  --red: #FF453A;
  --red-d: #C2302A;
  --orange: #FF9F0A;
  --blue: #0A84FF;
  --blue-d: #0060C0;
  color-scheme: dark;
}
:root[data-theme="light"] { color-scheme: light; }

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--label);
  font: 17px/1.4 var(--font);
  letter-spacing: -0.01em;
  -webkit-font-smoothing: antialiased;
  overscroll-behavior-y: none;
}
button, input, select, textarea { font: inherit; color: inherit; letter-spacing: inherit; }
button { cursor: pointer; border: 0; background: none; padding: 0; }
a { color: var(--accent); text-decoration: none; }
h1, h2, h3, p { margin: 0; }
ul { margin: 4px 0; padding-left: 1.2em; }
:focus-visible { outline: 3px solid color-mix(in srgb, var(--accent) 60%, transparent); outline-offset: 2px; border-radius: 8px; }

/* ---------- Layout ---------- */

#app { min-height: 100dvh; }
.view {
  outline: none;
  max-width: 760px;
  margin: 0 auto;
  padding: calc(var(--safe-t) + 12px) 16px calc(var(--tabbar-h) + var(--safe-b) + 40px);
  min-height: 100dvh;
}
.boot { display: grid; place-items: center; min-height: 60dvh; }
.spinner {
  width: 28px; height: 28px; border-radius: 50%;
  border: 3px solid var(--fill); border-top-color: var(--accent);
  animation: spin .8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* Floating glass tab bar (phone) */
.nav {
  position: fixed; z-index: 50;
  left: 50%; transform: translateX(-50%);
  bottom: calc(var(--safe-b) + 10px);
  display: flex; gap: 2px; padding: 6px;
  width: min(420px, calc(100% - 32px));
  background: var(--glass);
  -webkit-backdrop-filter: saturate(180%) blur(24px);
  backdrop-filter: saturate(180%) blur(24px);
  border: 0.5px solid var(--glass-border);
  border-radius: 999px;
  box-shadow: var(--shadow-lg);
  transition: transform .35s cubic-bezier(.2,.8,.2,1), opacity .25s;
}
.nav-brand { display: none; }
.nav a {
  flex: 1;
  display: flex; flex-direction: column; align-items: center; gap: 1px;
  padding: 7px 0 5px;
  border-radius: 999px;
  color: var(--label2);
  font-size: 10.5px; font-weight: 600;
  transition: background .2s, color .2s;
}
.nav a svg { width: 24px; height: 24px; fill: currentColor; fill-rule: evenodd; }
.nav a.active { color: var(--accent); background: var(--fill2); }
body.immersive .nav { transform: translate(-50%, 140%); opacity: 0; pointer-events: none; }
body.immersive .view { padding-bottom: calc(var(--safe-b) + 24px); }

/* Sidebar (iPad landscape / Mac) */
@media (min-width: 960px) {
  .nav {
    left: 0; top: 0; bottom: 0; transform: none;
    width: 250px; flex-direction: column; gap: 4px;
    padding: calc(var(--safe-t) + 20px) 14px 20px;
    border-radius: 0; border: 0; border-right: 0.5px solid var(--sep);
    box-shadow: none;
    background: var(--bg-elev);
  }
  .nav-brand {
    display: flex; align-items: center; gap: 10px;
    font: 700 22px var(--font-round); letter-spacing: -0.02em;
    padding: 0 10px 18px;
  }
  .nav-brand img { border-radius: 8px; }
  .nav a {
    flex: 0; flex-direction: row; gap: 12px;
    padding: 10px 12px; border-radius: 12px;
    font-size: 16px; font-weight: 500; color: var(--label);
  }
  .nav a svg { width: 22px; height: 22px; color: var(--accent); }
  .nav a.active { background: var(--accent); color: #fff; }
  .nav a.active svg { color: #fff; }
  .view { margin-left: 250px; margin-right: 0; max-width: none; padding: 32px 48px 48px; }
  .view > * { max-width: 920px; margin-left: auto; margin-right: auto; }
  body.immersive .nav { transform: translateX(-100%); }
  body.immersive .view { margin-left: 0; }
}

/* ---------- Typography ---------- */

.large-title { font: 800 34px/1.15 var(--font-round); letter-spacing: -0.025em; margin: 6px 0 2px; }
.subtitle { color: var(--label2); font-size: 15px; }
.section-title {
  font: 700 22px/1.2 var(--font-round); letter-spacing: -0.02em;
  margin: 28px 0 10px; display: flex; align-items: baseline; justify-content: space-between; gap: 8px;
}
.section-title a, .section-title button { font: 500 15px var(--font); color: var(--accent); }
.caption { font-size: 13px; color: var(--label2); }
.footnote { font-size: 13px; color: var(--label2); padding: 8px 16px 0; }
.mono { font-variant-numeric: tabular-nums; }

/* ---------- Header row ---------- */

.top { display: flex; align-items: flex-start; justify-content: space-between; gap: 12px; }
.chips { display: flex; gap: 8px; flex-shrink: 0; padding-top: 8px; }
.chip {
  display: inline-flex; align-items: center; gap: 5px;
  padding: 6px 12px; border-radius: 999px;
  background: var(--bg-elev); box-shadow: var(--shadow);
  font: 700 15px var(--font-round);
}
.chip.flame { color: var(--flame); }
.chip.flame.off { color: var(--label3); filter: grayscale(1); }
.chip.xp { color: var(--orange); }

.back {
  display: inline-flex; align-items: center; gap: 2px;
  color: var(--accent); font-size: 17px; margin: 4px 0 8px -6px; padding: 6px;
}
.back svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 2.6; stroke-linecap: round; stroke-linejoin: round; }

/* ---------- Cards & lists ---------- */

.card {
  background: var(--bg-elev);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 18px;
}
.card + .card { margin-top: 12px; }

.list { background: var(--bg-elev); border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; }
.row {
  display: flex; align-items: center; gap: 12px;
  padding: 12px 16px; min-height: 52px;
  position: relative; width: 100%; text-align: left;
  color: var(--label);
}
.row + .row::before {
  content: ""; position: absolute; top: 0; right: 0; left: 16px;
  border-top: 0.5px solid var(--sep);
}
.row.has-icon + .row.has-icon::before { left: 60px; }
a.row:active, button.row:active { background: var(--fill2); }
.row .grow { flex: 1; min-width: 0; }
.row .title { font-weight: 500; overflow: hidden; text-overflow: ellipsis; }
.row .sub { font-size: 14px; color: var(--label2); margin-top: 1px; }
.row .value { color: var(--label2); font-variant-numeric: tabular-nums; }
.row .chev { width: 8px; height: 14px; flex-shrink: 0; fill: none; stroke: var(--label3); stroke-width: 2.4; stroke-linecap: round; stroke-linejoin: round; }
.row select, .row input[type="date"], .row input[type="text"] {
  background: var(--fill2); border: 0; border-radius: 10px; padding: 7px 10px; font-size: 16px; max-width: 55%;
}
.row input[type="text"] { flex: 1; max-width: none; }
.row.danger { color: var(--red); justify-content: center; font-weight: 500; }
.row.action { color: var(--accent); font-weight: 500; }

.icon-tile {
  width: 34px; height: 34px; border-radius: 9px; flex-shrink: 0;
  display: grid; place-items: center; font-size: 19px;
  background: var(--tile, var(--accent));
  box-shadow: inset 0 0 0 0.5px rgba(0,0,0,.06);
}
.icon-tile.lg { width: 56px; height: 56px; border-radius: 15px; font-size: 30px; }
.icon-tile.xl { width: 72px; height: 72px; border-radius: 19px; font-size: 40px; }

.badge {
  min-width: 24px; height: 24px; padding: 0 8px; border-radius: 999px;
  display: inline-grid; place-items: center;
  background: var(--red); color: #fff; font: 700 13px var(--font-round);
}
.badge.gray { background: var(--fill); color: var(--label2); }
.badge.blue { background: var(--accent); }

/* Toggle switch */
.switch { position: relative; width: 51px; height: 31px; flex-shrink: 0; }
.switch input { position: absolute; opacity: 0; inset: 0; margin: 0; cursor: pointer; z-index: 1; }
.switch span {
  position: absolute; inset: 0; border-radius: 999px; background: var(--fill);
  transition: background .2s;
}
.switch span::after {
  content: ""; position: absolute; top: 2px; left: 2px; width: 27px; height: 27px; border-radius: 50%;
  background: #fff; box-shadow: 0 3px 8px rgba(0,0,0,.15), 0 1px 1px rgba(0,0,0,.16);
  transition: transform .25s cubic-bezier(.3,.7,.3,1.2);
}
.switch input:checked + span { background: var(--green); }
.switch input:checked + span::after { transform: translateX(20px); }

/* Segmented control */
.segmented {
  display: flex; padding: 2px; border-radius: 10px; background: var(--fill2); gap: 2px;
}
.segmented button {
  flex: 1; padding: 7px 10px; border-radius: 8px; font-size: 14px; font-weight: 500; color: var(--label);
  transition: background .2s, box-shadow .2s;
}
.segmented button.on { background: var(--bg-elev); box-shadow: 0 3px 8px rgba(0,0,0,.12), 0 1px 1px rgba(0,0,0,.04); font-weight: 600; }
:root[data-theme="dark"] .segmented button.on { background: #636366; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .segmented button.on { background: #636366; } }

/* ---------- Buttons (chunky, Duolingo-ish) ---------- */

.btn {
  --c: var(--accent); --cd: var(--blue-d);
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 14px 22px; min-height: 52px;
  border-radius: 16px;
  background: var(--c); color: #fff;
  font: 700 17px var(--font-round); letter-spacing: 0;
  box-shadow: 0 4px 0 var(--cd);
  transform: translateY(0);
  transition: transform .08s, box-shadow .08s, filter .2s;
  user-select: none; -webkit-user-select: none;
}
.btn:active { transform: translateY(4px); box-shadow: 0 0 0 var(--cd); }
.btn:disabled { filter: grayscale(1) opacity(.5); pointer-events: none; }
.btn.block { width: 100%; }
.btn.green { --c: var(--green); --cd: var(--green-d); }
.btn.red { --c: var(--red); --cd: var(--red-d); }
.btn.orange { --c: var(--orange); --cd: var(--orange-d); }
.btn.secondary { --c: var(--bg-elev); --cd: var(--sep); color: var(--accent); box-shadow: 0 4px 0 var(--cd), inset 0 0 0 1.5px var(--sep); }
.btn.secondary:active { box-shadow: 0 0 0 var(--cd), inset 0 0 0 1.5px var(--sep); }
.btn.plain { --cd: transparent; background: var(--fill2); color: var(--accent); box-shadow: none; }
.btn.small { min-height: 40px; padding: 8px 16px; font-size: 15px; border-radius: 12px; }
.btn-row { display: flex; gap: 10px; margin-top: 14px; }
.btn-row > .btn { flex: 1; }

.icon-btn {
  width: 40px; height: 40px; border-radius: 50%;
  display: inline-grid; place-items: center;
  background: var(--fill2); color: var(--label2);
}
.icon-btn svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 2.4; stroke-linecap: round; stroke-linejoin: round; }
.icon-btn.speak { color: var(--accent); background: color-mix(in srgb, var(--accent) 14%, transparent); }
.icon-btn.speak svg { fill: currentColor; stroke: none; }

/* ---------- Home ---------- */

.goal { display: flex; align-items: center; gap: 16px; }
.goal .ring text { font: 700 15px var(--font-round); fill: var(--label); }
.goal h3 { font: 700 19px var(--font-round); }
.goal-done { color: var(--green); }

.hero {
  position: relative; overflow: hidden;
  border-radius: var(--radius);
  padding: 22px;
  color: #fff;
  background:
    radial-gradient(120% 140% at 100% 0%, rgba(255,255,255,.22), transparent 50%),
    linear-gradient(135deg, #0A84FF 0%, #5E5CE6 55%, #BF5AF2 100%);
  box-shadow: 0 12px 30px rgba(10, 132, 255, .28);
}
.hero.done { background: radial-gradient(120% 140% at 100% 0%, rgba(255,255,255,.25), transparent 50%), linear-gradient(135deg, #30D158, #00C7BE); box-shadow: 0 12px 30px rgba(48, 209, 88, .25); }
.hero h2 { font: 800 28px/1.1 var(--font-round); letter-spacing: -0.02em; }
.hero p { opacity: .9; margin: 6px 0 16px; font-size: 16px; }
.hero .btn { --c: #fff; --cd: rgba(0,0,0,.18); color: #3634A3; }
.hero.done .btn { color: #1E8E3E; }
.hero .deco { position: absolute; right: -6px; bottom: -18px; font-size: 96px; opacity: .25; transform: rotate(-12deg); pointer-events: none; }
.hero-stats { display: flex; gap: 18px; margin: 10px 0 16px; }
.hero-stats div { display: flex; flex-direction: column; }
.hero-stats b { font: 800 28px var(--font-round); line-height: 1; }
.hero-stats span { font-size: 13px; opacity: .85; }

.scroller {
  display: flex; gap: 12px; overflow-x: auto; scroll-snap-type: x mandatory;
  margin: 0 -16px; padding: 4px 16px 8px; scrollbar-width: none;
}
.scroller::-webkit-scrollbar { display: none; }
.scroller > * { scroll-snap-align: start; flex-shrink: 0; }
.exam {
  width: 190px; padding: 14px 16px; border-radius: 18px;
  background: var(--bg-elev); box-shadow: var(--shadow);
  border-left: 5px solid var(--tile, var(--accent));
}
.exam .days { font: 800 30px/1 var(--font-round); color: var(--tile, var(--accent)); }
.exam .days small { font-size: 15px; font-weight: 700; }
.exam .t { font-weight: 600; margin-top: 6px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.exam.add { display: grid; place-items: center; border: 2px dashed var(--sep); background: transparent; box-shadow: none; color: var(--accent); font-weight: 600; text-align: center; }

.quick { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.quick a {
  display: flex; flex-direction: column; gap: 10px;
  padding: 16px; border-radius: var(--radius);
  background: var(--bg-elev); box-shadow: var(--shadow); color: var(--label);
  transition: transform .15s;
}
.quick a:active { transform: scale(.97); }
.quick b { font: 700 17px var(--font-round); }
.quick span.caption { margin-top: -6px; }

/* ---------- Subjects grid ---------- */

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 12px; }
.subject-tile {
  position: relative; display: flex; flex-direction: column; gap: 12px;
  padding: 16px; border-radius: var(--radius);
  background: var(--bg-elev); box-shadow: var(--shadow); color: var(--label);
  overflow: hidden; transition: transform .15s;
}
.subject-tile:active { transform: scale(.97); }
.subject-tile::after {
  content: ""; position: absolute; right: -30px; top: -30px; width: 110px; height: 110px; border-radius: 50%;
  background: var(--tile); opacity: .12;
}
.subject-tile b { font: 700 18px var(--font-round); }
.subject-tile .badge { position: absolute; top: 14px; right: 14px; z-index: 1; }

.bar { height: 8px; border-radius: 999px; background: var(--fill2); overflow: hidden; display: flex; }
.bar i { display: block; height: 100%; transition: width .5s cubic-bezier(.2,.8,.2,1); }
.bar i.m { background: var(--tile, var(--green)); }
.bar i.l { background: color-mix(in srgb, var(--tile, var(--green)) 40%, transparent); }

.subject-head { display: flex; align-items: center; gap: 16px; margin: 6px 0 4px; }
.subject-head h1 { font: 800 30px/1.1 var(--font-round); letter-spacing: -0.02em; }

.stat-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; text-align: center; }
.stat-row b { display: block; font: 800 24px var(--font-round); }
.stat-row span { font-size: 12px; color: var(--label2); }

/* ---------- Card browser ---------- */
details.cardrow { padding: 0 16px; }
details.cardrow + details.cardrow { border-top: 0.5px solid var(--sep); }
details.cardrow summary { list-style: none; padding: 12px 0; cursor: pointer; display: flex; gap: 10px; align-items: center; }
details.cardrow summary::-webkit-details-marker { display: none; }
details.cardrow summary .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--fill); flex-shrink: 0; }
details.cardrow summary .dot.l { background: var(--orange); }
details.cardrow summary .dot.m { background: var(--green); }
details.cardrow .ans { padding: 0 0 14px 18px; color: var(--label2); font-size: 15px; }

/* ---------- Session (review & quiz) ---------- */

.session-top {
  display: flex; align-items: center; gap: 12px;
  position: sticky; top: 0; z-index: 5;
  padding: calc(var(--safe-t) + 8px) 0 10px;
  margin-top: calc(-1 * (var(--safe-t) + 12px));
  background: linear-gradient(var(--bg) 70%, transparent);
}
.progress { flex: 1; height: 14px; border-radius: 999px; background: var(--fill2); overflow: hidden; }
.progress i {
  display: block; height: 100%; border-radius: 999px;
  background: linear-gradient(90deg, var(--green), #7EE36B);
  box-shadow: inset 0 -3px 0 rgba(0,0,0,.08), inset 0 3px 0 rgba(255,255,255,.3);
  transition: width .45s cubic-bezier(.2,.8,.2,1);
}
.session-top .count { font: 700 15px var(--font-round); color: var(--label2); min-width: 44px; text-align: right; }

.flash {
  margin-top: 8px;
  min-height: 46dvh;
  display: flex; flex-direction: column;
  background: var(--bg-elev);
  border-radius: 28px;
  box-shadow: var(--shadow-lg);
  padding: 20px 22px 24px;
  animation: cardIn .35s cubic-bezier(.2,.8,.2,1);
}
@keyframes cardIn { from { opacity: 0; transform: translateY(14px) scale(.98); } }
.flash .meta { display: flex; align-items: center; gap: 8px; font-size: 13px; color: var(--label2); }
.flash .meta .pill { padding: 3px 10px; border-radius: 999px; font-weight: 600; color: var(--tile); background: color-mix(in srgb, var(--tile) 14%, transparent); }
.flash .meta .state { margin-left: auto; font-weight: 600; }
.flash .front, .flash .back { flex: 1; display: flex; flex-direction: column; justify-content: center; align-items: center; text-align: center; gap: 10px; padding: 12px 0; }
.flash .front .q { font: 650 24px/1.3 var(--font-round); letter-spacing: -0.01em; }
.flash .front .q.long { font-size: 19px; font-weight: 600; }
.flash .back { border-top: 1.5px dashed var(--sep); animation: reveal .3s ease-out; }
@keyframes reveal { from { opacity: 0; transform: translateY(-6px); } }
.flash .back .a { font: 600 21px/1.35 var(--font-round); }
.flash .back .a.long { font: 400 17px/1.45 var(--font); text-align: left; align-self: stretch; }
.flash .example { font-size: 15px; color: var(--label2); font-style: italic; display: flex; align-items: center; gap: 8px; text-align: left; }
.flash .note { font-size: 14px; color: var(--label2); background: var(--fill2); padding: 6px 12px; border-radius: 10px; }
.flash .hint-btn { color: var(--accent); font-size: 15px; font-weight: 500; }
.word-row { display: flex; align-items: center; gap: 12px; justify-content: center; flex-wrap: wrap; }

.dock { margin-top: 18px; }
.rate { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.rate .btn { flex-direction: column; gap: 0; padding: 10px 4px; min-height: 64px; font-size: 16px; }
.rate .btn small { font: 600 12px var(--font); opacity: .9; }
.rate .btn kbd { display: none; }
@media (hover: hover) and (pointer: fine) {
  .rate .btn kbd, .dock .btn kbd { display: inline; font: 600 11px var(--font); opacity: .6; margin-top: 2px; }
}
.dock .btn kbd { display: none; }

/* Quiz */
.qtext { font: 650 22px/1.35 var(--font-round); letter-spacing: -0.01em; margin: 18px 0 18px; }
.qtext.long { font-size: 18px; font-weight: 600; }
.options { display: grid; gap: 10px; }
.opt {
  display: flex; align-items: center; gap: 12px; text-align: left;
  padding: 14px 16px; border-radius: 16px; min-height: 58px;
  background: var(--bg-elev);
  box-shadow: 0 3px 0 var(--sep), inset 0 0 0 2px var(--sep);
  transition: transform .08s, box-shadow .15s, background .15s;
  font-size: 17px;
}
.opt:active { transform: translateY(2px); }
.opt .k {
  width: 28px; height: 28px; border-radius: 8px; flex-shrink: 0;
  display: grid; place-items: center; font: 700 14px var(--font-round);
  box-shadow: inset 0 0 0 2px var(--sep); color: var(--label2);
}
.opt.sel { background: color-mix(in srgb, var(--accent) 10%, var(--bg-elev)); box-shadow: 0 3px 0 var(--accent), inset 0 0 0 2px var(--accent); }
.opt.sel .k { background: var(--accent); color: #fff; box-shadow: none; }
.opt.right { background: color-mix(in srgb, var(--green) 14%, var(--bg-elev)); box-shadow: 0 3px 0 var(--green), inset 0 0 0 2px var(--green); }
.opt.right .k { background: var(--green); color: #fff; box-shadow: none; }
.opt.wrong { background: color-mix(in srgb, var(--red) 12%, var(--bg-elev)); box-shadow: 0 3px 0 var(--red), inset 0 0 0 2px var(--red); animation: shake .35s; }
.opt.wrong .k { background: var(--red); color: #fff; box-shadow: none; }
.options.locked .opt { pointer-events: none; }
@keyframes shake { 20%, 60% { transform: translateX(-5px); } 40%, 80% { transform: translateX(5px); } }

.answer-field { display: flex; align-items: center; gap: 10px; }
.answer-field input {
  flex: 1; min-width: 0;
  font-size: 20px; padding: 14px 16px; border-radius: 16px; border: 0;
  background: var(--bg-elev); box-shadow: inset 0 0 0 2px var(--sep);
  outline: none;
}
.answer-field input:focus { box-shadow: inset 0 0 0 2px var(--accent); }
.answer-field .unit { font: 700 18px var(--font-round); color: var(--label2); }
.answer-field.right input { box-shadow: inset 0 0 0 2px var(--green); }
.answer-field.wrong input { box-shadow: inset 0 0 0 2px var(--red); animation: shake .35s; }

.feedback {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 60;
  padding: 18px 20px calc(var(--safe-b) + 18px);
  border-radius: 24px 24px 0 0;
  background: var(--bg-elev); box-shadow: 0 -10px 40px rgba(0,0,0,.15);
  animation: sheetUp .3s cubic-bezier(.2,.8,.2,1);
  max-height: 70dvh; overflow-y: auto;
}
@media (min-width: 960px) { .feedback { left: 250px; } body.immersive .feedback { left: 0; } }
.feedback > div { max-width: 728px; margin: 0 auto; }
@keyframes sheetUp { from { transform: translateY(100%); } }
.feedback.ok { background: color-mix(in srgb, var(--green) 16%, var(--bg-elev)); }
.feedback.bad { background: color-mix(in srgb, var(--red) 13%, var(--bg-elev)); }
.feedback h3 { font: 800 22px var(--font-round); display: flex; align-items: center; gap: 8px; }
.feedback.ok h3 { color: var(--green-d); }
.feedback.bad h3 { color: var(--red); }
:root[data-theme="dark"] .feedback.ok h3 { color: var(--green); }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .feedback.ok h3 { color: var(--green); } }
.feedback .sol { margin-top: 6px; font-weight: 600; }
.feedback .also { margin-top: 6px; font-size: 15px; color: var(--label2); }
.feedback .btn.plain { margin-top: 10px; }
.feedback .expl { margin-top: 8px; font-size: 15px; color: var(--label2); line-height: 1.5; }
.feedback .btn { margin-top: 14px; }
.xp-pop { display: inline-block; font: 800 15px var(--font-round); color: var(--orange); animation: pop .5s cubic-bezier(.3,1.6,.5,1); }
@keyframes pop { from { transform: scale(.3); opacity: 0; } }

/* Written exercises (Übungsblatt) */
.exercise { display: grid; gap: 14px; }
.ex-field {
  background: var(--bg-elev); border-radius: 18px; padding: 12px 14px;
  box-shadow: inset 0 0 0 2px var(--sep); transition: box-shadow .2s, background .2s;
}
.ex-field.ok { box-shadow: inset 0 0 0 2px var(--green); background: color-mix(in srgb, var(--green) 8%, var(--bg-elev)); }
.ex-field.bad { box-shadow: inset 0 0 0 2px var(--red); background: color-mix(in srgb, var(--red) 6%, var(--bg-elev)); }
.ex-field label { display: block; font: 700 15px var(--font-round); margin-bottom: 6px; }
.ex-field textarea {
  width: 100%; resize: vertical; min-height: 48px; border: 0; outline: none;
  background: var(--fill2); border-radius: 12px; padding: 10px 12px; font-size: 16px; line-height: 1.4;
}
.ex-field textarea:focus { box-shadow: inset 0 0 0 2px var(--accent); }
.ex-field textarea[readonly] { opacity: .85; }
.ex-proof { margin-top: 10px; padding: 10px 12px; border-radius: 12px; font-size: 15px; line-height: 1.5;
  background: color-mix(in srgb, var(--orange) 12%, transparent); }
.ex-proof > span { display: block; font: 700 12px var(--font-round); text-transform: uppercase; letter-spacing: .04em; color: var(--orange); margin-bottom: 2px; }
.ex-proof del { color: var(--red); text-decoration-thickness: 2px; }
.ex-proof ins { color: var(--green-d); text-decoration: none; font-weight: 700; background: color-mix(in srgb, var(--green) 18%, transparent); border-radius: 4px; padding: 0 2px; margin-left: 2px; }
.ex-proof ul { margin: 6px 0 0; font-size: 13px; color: var(--label2); }
.ex-proof.clean { background: color-mix(in srgb, var(--green) 12%, transparent); color: var(--green-d); font-weight: 600; }
.ex-proof.off, .ex-proof.empty { background: var(--fill2); color: var(--label2); }
.ex-model { margin-top: 10px; padding: 10px 12px; border-radius: 12px; font-size: 15px; line-height: 1.45;
  background: color-mix(in srgb, var(--accent) 10%, transparent); }
.ex-model span { display: block; font: 700 12px var(--font-round); text-transform: uppercase; letter-spacing: .04em; color: var(--accent); margin-bottom: 2px; }
.ex-mark { display: flex; gap: 8px; margin-top: 10px; }
.ex-mark button { flex: 1; padding: 9px 8px; border-radius: 12px; font-weight: 600; font-size: 15px;
  background: var(--fill2); color: var(--label2); }
.ex-mark button[data-val="1"].on { background: var(--green); color: #fff; }
.ex-mark button[data-val="0"].on { background: var(--red); color: #fff; }
.expl-card { font-size: 15px; color: var(--label2); line-height: 1.5; }

.timer { font: 700 15px var(--font-round); color: var(--label2); font-variant-numeric: tabular-nums; }
.timer.low { color: var(--red); }

/* Summary */
.summary { text-align: center; padding-top: 6dvh; }
.summary .big-emoji { font-size: 84px; line-height: 1; animation: pop .6s cubic-bezier(.3,1.6,.5,1); }
.summary h1 { font: 800 32px var(--font-round); margin: 14px 0 6px; letter-spacing: -0.02em; }
.summary .tiles { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 24px 0; }
.summary .tile { padding: 14px 6px; border-radius: 18px; border: 2px solid var(--tc, var(--sep)); }
.summary .tile .h { font: 800 12px var(--font-round); text-transform: uppercase; letter-spacing: .04em; color: var(--tc); }
.summary .tile b { display: block; font: 800 24px var(--font-round); margin-top: 4px; }
.grade { display: inline-grid; place-items: center; width: 96px; height: 96px; border-radius: 50%; font: 800 44px var(--font-round); color: #fff; background: var(--gc, var(--green)); box-shadow: 0 6px 0 rgba(0,0,0,.15); }
.review-list { text-align: left; margin-top: 18px; }
.review-list .item { padding: 14px 16px; }
.review-list .item + .item { border-top: 0.5px solid var(--sep); }
.review-list .yours { color: var(--red); font-size: 15px; }
.review-list .right { color: var(--green-d); font-size: 15px; font-weight: 600; }

/* ---------- Stats ---------- */

.tiles4 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; }
@media (min-width: 640px) { .tiles4 { grid-template-columns: repeat(4, 1fr); } }
.tiles4 .card { padding: 14px 16px; }
.tiles4 .card + .card { margin-top: 0; }
.tiles4 .v { font: 800 28px var(--font-round); letter-spacing: -0.02em; }
.tiles4 .l { font-size: 13px; color: var(--label2); }

.heat { display: grid; grid-auto-flow: column; grid-template-rows: repeat(7, 1fr); gap: 3px; overflow-x: auto; }
.heat i { width: 13px; height: 13px; border-radius: 3px; background: var(--fill2); }
.heat i.l1 { background: color-mix(in srgb, var(--green) 30%, transparent); }
.heat i.l2 { background: color-mix(in srgb, var(--green) 55%, transparent); }
.heat i.l3 { background: color-mix(in srgb, var(--green) 80%, transparent); }
.heat i.l4 { background: var(--green); }
.heat i.today { outline: 2px solid var(--label2); outline-offset: -1px; }

.bars { display: flex; align-items: flex-end; gap: 8px; height: 130px; padding-top: 18px; }
.bars .b { flex: 1; display: flex; flex-direction: column; align-items: center; gap: 6px; height: 100%; justify-content: flex-end; }
.bars .b i { display: block; width: 100%; max-width: 34px; border-radius: 6px 6px 3px 3px; background: var(--accent); min-height: 3px; transition: height .5s; }
.bars .b.today i { background: var(--orange); }
.bars .b span { font-size: 11px; color: var(--label2); }
.bars .b em { font-style: normal; font: 700 11px var(--font-round); color: var(--label2); }

.legend { display: flex; gap: 14px; font-size: 12px; color: var(--label2); margin-top: 10px; flex-wrap: wrap; }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: 5px; vertical-align: -1px; }

/* ---------- Misc ---------- */

.empty { text-align: center; padding: 40px 20px; color: var(--label2); }
.empty .e { font-size: 56px; }
.empty h3 { color: var(--label); font: 700 20px var(--font-round); margin: 10px 0 6px; }

#toast {
  position: fixed; left: 50%; top: calc(var(--safe-t) + 12px); z-index: 100;
  transform: translate(-50%, -150%);
  background: var(--glass); -webkit-backdrop-filter: blur(20px); backdrop-filter: blur(20px);
  border: 0.5px solid var(--glass-border);
  padding: 10px 18px; border-radius: 999px; box-shadow: var(--shadow-lg);
  font-weight: 600; font-size: 15px;
  transition: transform .35s cubic-bezier(.2,.8,.2,1);
  pointer-events: none; max-width: calc(100% - 32px); text-align: center;
}
#toast.show { transform: translate(-50%, 0); }
#confetti { position: fixed; inset: 0; width: 100%; height: 100%; pointer-events: none; z-index: 200; display: none; }

.sheet-backdrop { position: fixed; inset: 0; background: rgba(0,0,0,.35); z-index: 80; animation: fade .2s; display: grid; place-items: end center; }
@media (min-width: 640px) { .sheet-backdrop { place-items: center; } }
@keyframes fade { from { opacity: 0; } }
.sheet {
  width: 100%; max-width: 520px; background: var(--bg); border-radius: 26px 26px 0 0;
  padding: 10px 16px calc(var(--safe-b) + 20px); animation: sheetUp .3s cubic-bezier(.2,.8,.2,1);
  max-height: 90dvh; overflow-y: auto;
}
@media (min-width: 640px) { .sheet { border-radius: 26px; padding-bottom: 20px; } }
.sheet .grabber { width: 36px; height: 5px; border-radius: 3px; background: var(--fill); margin: 0 auto 10px; }
.sheet h2 { font: 700 20px var(--font-round); text-align: center; margin-bottom: 14px; }

.fade-in { animation: viewIn .28s ease-out; }
@keyframes viewIn { from { opacity: 0; transform: translateY(6px); } }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}