/* Physics scenes: a full-screen canvas with soft panels floating over it.
   The scene is a dark night window, so glowing particles and waves stand out; the panels and the card keep the
   warm pastel colours and the Nunito font of the other lessons. */

:root {
  --night: #15122b;        /* page behind the canvas */
  --panel: rgba(28, 23, 56, 0.72);
  --panel-border: rgba(255, 255, 255, 0.16);
  --light: #fdf6ec;        /* text on the dark panels */
  --dim: #c9c0e6;
  --main: #ffb86b;         /* warm apricot: main button, active choice, slider */
  --main-dark: #e8954a;
  --ink: #3d2b2f;          /* text on the cream card */
  --muted: #8b7576;
  --cream: #fff8ec;
  --cream-border: #eadfcd;
}

* { box-sizing: border-box; }

html, body {
  height: 100%;
  margin: 0;
  overflow: hidden;
  overscroll-behavior: none;
}

body {
  background: var(--night);
  color: var(--light);
  font-family: "Nunito", ui-rounded, "SF Pro Rounded", system-ui, -apple-system, sans-serif;
  font-weight: 600;
  -webkit-tap-highlight-color: transparent;
  -webkit-user-select: none;
  user-select: none;
}

button {
  font: inherit;
  color: inherit;
  cursor: pointer;
}

.stage {
  position: fixed;
  inset: 0;
  display: block;
  width: 100%;
  height: 100%;
  touch-action: none;
}

/* ---------- Panels over the scene ---------- */

.top {
  position: fixed;
  top: calc(12px + env(safe-area-inset-top));
  left: calc(12px + env(safe-area-inset-left));
  right: calc(12px + env(safe-area-inset-right));
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
  pointer-events: none;
}
.top > * { pointer-events: auto; }

.heading {
  max-width: min(560px, calc(100% - 60px));
  padding: 8px 16px 10px;
  border-radius: 20px;
  background: var(--panel);
  border: 2px solid var(--panel-border);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}

.title {
  margin: 0;
  font-size: 20px;
  font-weight: 900;
  line-height: 1.25;
}

.question {
  margin: 2px 0 0;
  color: var(--dim);
  font-size: 15px;
  line-height: 1.35;
}
.question:empty { display: none; }

.chip {
  min-width: 48px;
  min-height: 48px;
  padding: 0 16px;
  border-radius: 999px;
  background: var(--panel);
  border: 2px solid var(--panel-border);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  font-size: 17px;
  font-weight: 800;
  line-height: 1;
  white-space: nowrap;
  transition: transform 0.1s, background 0.15s;
}
.chip:hover { background: rgba(48, 40, 90, 0.85); }
.chip:active { transform: translateY(2px); }
.chip.round { padding: 0; font-size: 22px; font-weight: 900; }
.chip.primary { background: var(--main); border-color: var(--main-dark); color: var(--ink); }
.chip.primary:hover { background: #ffc583; }
.chip.on { background: var(--main); border-color: var(--main-dark); color: var(--ink); }
.chip:disabled { opacity: 0.45; cursor: default; transform: none; }

.readout {
  position: fixed;
  top: calc(72px + env(safe-area-inset-top));
  right: calc(12px + env(safe-area-inset-right));
  max-width: 46vw;
  padding: 8px 14px;
  border-radius: 16px;
  background: var(--panel);
  border: 2px solid var(--panel-border);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  font-size: 15px;
  font-weight: 800;
  line-height: 1.45;
  white-space: pre-line;
  text-align: right;
  font-variant-numeric: tabular-nums;
  pointer-events: none;
}

.hint {
  position: fixed;
  left: 50%;
  bottom: 92px; /* common.ts moves it just above the controls */
  transform: translateX(-50%);
  max-width: calc(100% - 32px);
  margin: 0;
  padding: 10px 18px;
  border-radius: 999px;
  background: rgba(255, 248, 236, 0.92);
  color: var(--ink);
  font-size: 17px;
  font-weight: 800;
  text-align: center;
  pointer-events: none;
  transition: opacity 0.6s;
}
.hint.fade { opacity: 0; }

.no-gl {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: min(440px, calc(100% - 32px));
  margin: 0;
  padding: 20px 24px;
  border-radius: 24px;
  background: var(--cream);
  color: var(--ink);
  font-size: 18px;
  line-height: 1.45;
  text-align: center;
}

/* ---------- Controls: bottom bar, clear of the 🏠 button in the bottom-left corner ---------- */

.controls {
  position: fixed;
  left: 0;
  right: 0;
  bottom: calc(14px + env(safe-area-inset-bottom));
  padding: 0 172px; /* clear of the 🏠 «Все уроки» button on both sides, so the bar stays centred */
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 8px;
  pointer-events: none;
}
.controls > * { pointer-events: auto; }

.choice {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  padding: 3px;
  gap: 3px;
  border-radius: 24px;
  background: var(--panel);
  border: 2px solid var(--panel-border);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}
.choice .chip {
  min-height: 40px;
  padding: 0 14px;
  background: transparent;
  border-color: transparent;
  -webkit-backdrop-filter: none;
  backdrop-filter: none;
}
.choice .chip.on { background: var(--main); border-color: var(--main-dark); color: var(--ink); }

.slider {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 48px;
  padding: 0 16px;
  border-radius: 999px;
  background: var(--panel);
  border: 2px solid var(--panel-border);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  font-size: 16px;
  font-weight: 800;
}
.slider input {
  width: 150px;
  height: 28px;
  margin: 0;
  accent-color: var(--main);
  cursor: pointer;
}
.slider output {
  min-width: 3ch;
  color: var(--main);
  font-variant-numeric: tabular-nums;
}

/* ---------- «Что тут происходит?» ---------- */

.overlay {
  position: fixed;
  inset: 0;
  z-index: 10;
  display: grid;
  place-items: center;
  padding: 16px;
  background: rgba(10, 8, 25, 0.55);
}
.overlay[hidden] { display: none; }

.card {
  width: min(540px, 100%);
  max-height: calc(100vh - 32px);
  max-height: calc(100dvh - 32px);
  overflow-y: auto;
  padding: 22px 26px 24px;
  border-radius: 28px;
  background: var(--cream);
  border: 3px solid var(--cream-border);
  box-shadow: 0 8px 0 var(--cream-border);
  color: var(--ink);
  text-align: center;
  -webkit-user-select: text;
  user-select: text;
}
.card-icon { font-size: 52px; line-height: 1.1; }
.card h2 { margin: 6px 0 10px; font-size: 26px; font-weight: 900; }
.about-text { text-align: left; font-size: 18px; line-height: 1.5; }
.about-text p { margin: 0 0 12px; }

.btn {
  min-height: 52px;
  padding: 0 28px;
  margin-top: 6px;
  border-radius: 999px;
  border: 3px solid var(--cream-border);
  background: #fff;
  font-size: 19px;
  font-weight: 900;
  box-shadow: 0 4px 0 var(--cream-border);
}
.btn.primary { background: var(--main); border-color: var(--main-dark); box-shadow: 0 4px 0 var(--main-dark); }
.btn:active { transform: translateY(3px); box-shadow: 0 1px 0 var(--main-dark); }

/* ---------- Phones ---------- */

@media (max-width: 700px) {
  .title { font-size: 17px; }
  .question { font-size: 14px; }
  .heading { padding: 6px 12px 8px; }
  .readout { top: calc(66px + env(safe-area-inset-top)); font-size: 13px; padding: 6px 10px; }
  /* the 🏠 button is a 48px circle on the left: keep the bar to its right */
  .controls { padding: 0 12px 0 72px; justify-content: flex-start; gap: 6px; }
  .chip { min-height: 44px; font-size: 16px; padding: 0 12px; }
  .choice .chip { min-height: 38px; padding: 0 10px; }
  .slider { min-height: 44px; padding: 0 12px; font-size: 14px; gap: 8px; }
  .slider input { width: 110px; }
  .hint { font-size: 15px; }
  .about-text { font-size: 17px; }
}

@media (prefers-reduced-motion: reduce) {
  .chip, .hint { transition: none; }
}