/* Lenia explorer. The world covers the viewport; the interface floats over it in small panels that open on demand.
   Panel colours are chosen so text keeps at least 4.5:1 contrast against the panel composited over the brightest colour of
   either colour map (see docs/reports, M2 contrast table). */
:root {
  color-scheme: dark;
  --bg: #0b0d12;
  --text: #e7ecf6;
  --muted: #b6c0d4;          /* lighter than before: it must also pass 4.5:1 on glass over a bright world */
  --accent: #3fd6c8;
  --accent-ink: #04201e;
  --amber: #ffc477;
  --danger: #ff8f8f;
  --line: rgba(200, 215, 240, 0.16);
  --line-strong: rgba(200, 215, 240, 0.32);
  --glass: rgba(13, 18, 28, 0.80); /* alpha 0.80: the contrast floor, see the header comment */
  --solid: #111826;
  --panel-bg: var(--glass);
  --blur: blur(14px) saturate(1.1);
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  --radius: 14px;
  --gap: 12px;
  --rail: 44px;              /* touch target */
  --edge: 12px;
  --top: 64px;               /* panels start below the top bar */
  --bottom: 88px;            /* and end above the transport bar */
  --panel-w: 340px;
  --bn-font: "Noto Sans Bengali", "Nirmala UI", "Shonar Bangla", "Kohinoor Bangla", "Bangla Sangam MN", "Hind Siliguri", "Kalpurush", "Vrinda", sans-serif;
  --ui-font: system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", var(--bn-font);
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;          /* a full-screen app: panels scroll inside themselves */
  background: var(--bg);
  color: var(--text);
  font: 14px/1.5 var(--ui-font);
}

.bn, [lang="bn"] { font-family: var(--bn-font), var(--ui-font); line-height: 1.8; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---- the world ---- */
.app { position: fixed; inset: 0; }
.stage { position: absolute; inset: 0; background: var(--bg); }
#lenia-canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; touch-action: none; cursor: grab; }
#lenia-canvas.dragging { cursor: grabbing; }
#lenia-canvas.placing { cursor: crosshair; }
#lenia-canvas:focus-visible { outline: 2px solid var(--accent); outline-offset: -2px; }

/* ---- shared surfaces: glass, or solid when chosen, unsupported or reduced transparency is asked ---- */
.surface, .panel, .rail, .transport-bar, .status-chip, .icon-btn, .view-btns, .view-cell, .toasts, .tooltip, .show-ui {
  background: var(--panel-bg);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
}
.app[data-panels="solid"] { --panel-bg: var(--solid); --blur: none; }
.app[data-panels="solid"] ~ .tooltip, .app[data-panels="solid"] ~ .show-ui { --panel-bg: var(--solid); --blur: none; }
@supports not ((backdrop-filter: blur(1px)) or (-webkit-backdrop-filter: blur(1px))) {
  :root { --panel-bg: var(--solid); }
}
@media (prefers-reduced-transparency: reduce) {
  :root { --panel-bg: var(--solid); --blur: none; }
}

/* ---- buttons ---- */
.btn {
  font: inherit; color: var(--text); background: transparent; cursor: pointer; min-height: 40px;
  padding: 7px 14px; border-radius: 10px; border: 1px solid var(--line);
  transition: background 0.15s, border-color 0.15s;
}
.btn:hover:not(:disabled) { background: rgba(200, 215, 240, 0.12); border-color: var(--line-strong); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); font-weight: 650; }
.btn-primary:hover:not(:disabled) { background: #6fe6da; border-color: #6fe6da; }
.btn-ghost { border-color: transparent; color: var(--muted); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.seg-btn { font: inherit; font-size: 13px; color: var(--muted); background: transparent; border: 0; padding: 0 12px; min-height: 44px; min-width: 44px; cursor: pointer; }
.seg-btn + .seg-btn { border-left: 1px solid var(--line); }
.seg-btn:disabled { opacity: 0.45; cursor: not-allowed; }
.seg-btn[aria-pressed="true"] { background: rgba(63, 214, 200, 0.22); color: var(--text); }
.seg-wide { display: flex; }
.seg-wide .seg-btn { flex: 1; }

/* ---- top bar: wordmark, status chip, hide ---- */
.topbar {
  position: absolute; top: max(var(--edge), env(safe-area-inset-top, 0px)); left: max(var(--edge), env(safe-area-inset-left, 0px));
  right: max(var(--edge), env(safe-area-inset-right, 0px));
  display: flex; align-items: center; justify-content: space-between; gap: var(--gap); pointer-events: none;
}
.topbar > * { pointer-events: auto; }
.wordmark {
  font: 700 15px/1 var(--ui-font); letter-spacing: 0.34em; color: var(--text); background: transparent; border: 0;
  padding: 12px 10px; min-height: 44px; cursor: pointer; text-shadow: 0 1px 6px rgba(0, 0, 0, 0.6); border-radius: 10px;
}
.topbar-right { display: flex; align-items: center; gap: 8px; }
.status-chip {
  display: inline-flex; align-items: center; gap: 10px; min-height: 44px; padding: 0 14px; border-radius: 999px;
  font: 13px var(--ui-font); color: var(--text); cursor: pointer;
}
.status-chip .state { display: inline-flex; align-items: center; gap: 7px; }
.status-chip .state::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: var(--muted); }
.status-chip .state[data-state="running"]::before { background: var(--accent); }
.status-chip .state[data-state="paused"]::before { background: var(--amber); }
.chip-gen { color: var(--muted); font-variant-numeric: tabular-nums; }
.badge { font-size: 12px; padding: 2px 8px; border-radius: 999px; border: 1px solid rgba(255, 196, 119, 0.5); color: var(--amber); }
.icon-btn, .rail-btn {
  display: inline-grid; place-items: center; width: var(--rail); height: var(--rail); border-radius: 12px; color: var(--text); cursor: pointer;
}
.rail-btn { background: transparent; border: 0; box-shadow: none; -webkit-backdrop-filter: none; backdrop-filter: none; }
.icon-btn svg, .rail-btn svg { width: 22px; height: 22px; }
.rail-btn:hover, .icon-btn:hover { background: rgba(200, 215, 240, 0.12); }
.rail-btn[aria-expanded="true"] { background: rgba(63, 214, 200, 0.22); color: var(--accent); }

/* ---- rails ---- */
.rail {
  position: absolute; top: var(--top); bottom: var(--bottom); width: calc(var(--rail) + 8px);
  display: flex; flex-direction: column; gap: 6px; padding: 4px; border-radius: 16px; height: max-content; max-height: calc(100% - var(--top) - var(--bottom));
}
.rail-left { left: max(var(--edge), env(safe-area-inset-left, 0px)); }
.rail-right { right: max(var(--edge), env(safe-area-inset-right, 0px)); }
.rail-gap { height: 18px; flex: 0 0 auto; }

/* ---- floating panels ---- */
.panel {
  position: absolute; top: var(--top); width: min(var(--panel-w), calc(100vw - 2 * (var(--rail) + 3 * var(--edge))));
  max-height: calc(100% - var(--top) - var(--bottom)); display: flex; flex-direction: column; border-radius: var(--radius);
}
.panel[data-side="left"] { left: calc(max(var(--edge), env(safe-area-inset-left, 0px)) + var(--rail) + 8px + var(--edge)); }
.panel[data-side="right"] { right: calc(max(var(--edge), env(safe-area-inset-right, 0px)) + var(--rail) + 8px + var(--edge)); }
.panel:focus { outline: none; }
.panel-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 6px 6px 6px 16px; border-bottom: 1px solid var(--line); }
.panel-head h2 { margin: 0; font-size: 12px; font-weight: 650; letter-spacing: 0.12em; text-transform: uppercase; color: var(--muted); }
.panel-close { width: 44px; height: 44px; border: 0; background: transparent; color: var(--muted); font-size: 22px; line-height: 1; border-radius: 10px; cursor: pointer; }
.panel-close:hover { background: rgba(200, 215, 240, 0.12); color: var(--text); }
.panel-body { padding: 14px 16px 16px; overflow-y: auto; overscroll-behavior: contain; display: flex; flex-direction: column; gap: 10px; min-height: 0; }
.panel-body p { margin: 0; }
.panel-body h3 { margin: 6px 0 0; font-size: 12px; font-weight: 650; letter-spacing: 0.1em; text-transform: uppercase; color: var(--muted); }
.lede { color: var(--muted); }
.hint { color: var(--muted); font-size: 13px; }
.locked { color: var(--amber); }
.start { font-family: var(--mono); }
.row { display: flex; align-items: center; justify-content: space-between; gap: 10px; flex-wrap: wrap; }
.row-label { color: var(--muted); font-size: 13px; }
.place-row { justify-content: flex-start; }
#btn-place[aria-pressed="true"], #btn-add[aria-pressed="true"] { background: rgba(63, 214, 200, 0.22); border-color: var(--accent); }
details.more summary { cursor: pointer; color: var(--muted); font-size: 13px; min-height: 32px; display: flex; align-items: center; gap: 6px; }
details.more summary::before { content: "i"; display: inline-grid; place-items: center; width: 18px; height: 18px; border-radius: 50%; border: 1px solid var(--line-strong); font: 600 11px var(--mono); }
details.more[open] summary { color: var(--text); }
details.more > p { margin-top: 6px; }
.help-about .about-title { font: 700 15px/1 var(--ui-font); letter-spacing: 0.34em; }
.keys-list { margin: 0; padding-left: 18px; color: var(--muted); display: grid; gap: 4px; }
.keys { color: var(--muted); font-size: 12.5px; }
kbd { font: 11.5px var(--mono); padding: 1px 5px; border: 1px solid var(--line-strong); border-radius: 4px; color: var(--text); }

.facts { margin: 0; display: grid; gap: 6px; }
.facts div { display: flex; justify-content: space-between; gap: 12px; }
.facts dt { color: var(--muted); }
.facts dd { margin: 0; font: 12.5px var(--mono); text-align: right; font-variant-numeric: tabular-nums; }

.param { padding-bottom: 10px; border-bottom: 1px solid var(--line); }
.param-head { display: flex; justify-content: space-between; align-items: baseline; }
.param label { font-weight: 600; }
.sym { color: var(--accent); font-family: var(--mono); margin-right: 4px; }
.param output { font: 13px var(--mono); color: var(--accent); }
.param input[type="range"] { width: 100%; margin: 6px 0; min-height: 32px; accent-color: var(--accent); }
.fixed-note { color: var(--muted); font-size: 12.5px; }
.obs-chart { display: block; width: 100%; height: 96px; border: 1px solid var(--line); border-radius: 8px; background: rgba(5, 8, 14, 0.6); }

/* ---- transport bar (bottom centre) ---- */
.transport-bar {
  position: absolute; left: 50%; transform: translateX(-50%); bottom: max(16px, env(safe-area-inset-bottom, 0px));
  display: flex; align-items: center; gap: 8px; padding: 6px; border-radius: 16px; max-width: calc(100vw - 2 * var(--edge));
}
.transport-bar .btn { min-height: 44px; }
.transport-bar #btn-play { min-width: 88px; }
.transport-bar .row-label { padding-left: 4px; }
.bar-sep { width: 1px; align-self: stretch; margin: 6px 2px; background: var(--line); }

/* ---- view tools (bottom right) ---- */
.view-tools {
  position: absolute; right: max(16px, env(safe-area-inset-right, 0px)); bottom: max(16px, env(safe-area-inset-bottom, 0px));
  display: flex; flex-direction: column; align-items: flex-end; gap: 8px; pointer-events: none;
  background: none; border: 0; box-shadow: none; -webkit-backdrop-filter: none; backdrop-filter: none;
}
.view-tools > * { pointer-events: auto; }
.view-btns { display: flex; gap: 4px; padding: 4px; border-radius: 14px; }
.view-btn { min-width: 44px; min-height: 44px; padding: 0 12px; border-color: transparent; }
.view-cell { padding: 4px 10px; border-radius: 999px; font: 12px var(--mono); color: var(--muted); min-width: 13ch; text-align: right; }

/* ---- notes (top centre) ---- */
.toasts {
  position: absolute; top: calc(max(var(--edge), env(safe-area-inset-top, 0px)) + 52px); left: 50%; transform: translateX(-50%);
  display: flex; align-items: center; gap: 4px; padding: 4px 4px 4px 14px; border-radius: 12px; max-width: min(60ch, calc(100vw - 2 * var(--edge)));
}
.toast-text { margin: 0; color: var(--amber); font-size: 13px; }
.toast-close { width: 36px; height: 36px; border: 0; background: transparent; color: var(--muted); font-size: 20px; border-radius: 8px; cursor: pointer; flex: 0 0 auto; }

/* ---- tooltip ---- */
.tooltip {
  position: fixed; z-index: 40; padding: 6px 10px; border-radius: 8px; font-size: 12.5px; color: var(--text);
  max-width: 260px; pointer-events: auto;
}

/* ---- hidden interface ---- */
.app[data-ui="hidden"] .chrome { display: none !important; }
.show-ui {
  position: fixed; z-index: 30; top: max(var(--edge), env(safe-area-inset-top, 0px)); right: max(var(--edge), env(safe-area-inset-right, 0px));
  min-height: 44px; padding: 0 16px; border-radius: 999px; color: var(--text); font: inherit; cursor: pointer;
}

/* ---- guided tour ---- */
.tour { position: fixed; inset: 0; z-index: 20; pointer-events: none; }
.tour-backdrop { position: absolute; inset: 0; background: rgba(5, 7, 12, 0.72); opacity: 0; }
.tour-card {
  position: absolute; pointer-events: auto; background: var(--solid); border: 1px solid var(--line);
  border-radius: 14px; padding: 18px 20px; overflow: auto; box-shadow: 0 12px 40px rgba(0, 0, 0, 0.5);
}
.tour-card:focus { outline: none; }
.tour-card h2 { margin: 0 0 10px; font-size: 18px; }
.tour-card p { margin: 0 0 10px; }
.tour-progress { color: var(--muted); font: 12px var(--mono); margin-bottom: 6px !important; }
.tour-list { margin: 0 0 10px; padding-left: 18px; }
.tour-list li { margin-bottom: 4px; }
.tour-status { color: var(--amber); min-height: 1.5em; }
.tour-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; padding: 10px 0 0; position: sticky; bottom: -18px; background: var(--solid); }
.tour progress { width: 100%; height: 8px; accent-color: var(--accent); }
.tour[data-modal="true"] { pointer-events: auto; }
.tour[data-modal="true"] .tour-backdrop { opacity: 1; }
.tour[data-modal="true"] .tour-card { top: 50%; left: 50%; transform: translate(-50%, -50%); width: min(560px, calc(100vw - 24px)); max-height: calc(100% - 24px); }
/* Docked steps sit top-left, between the left rail and the open right panel, clear of the transport bar. */
.tour[data-modal="false"] .tour-card {
  top: var(--top); left: calc(max(var(--edge), env(safe-area-inset-left, 0px)) + var(--rail) + 8px + var(--edge));
  width: min(380px, calc(100vw - 2 * (var(--rail) + 3 * var(--edge)) - var(--panel-w) - var(--gap)));
  max-height: calc(100% - var(--top) - var(--bottom));
}
.spot { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---- fatal error ---- */
#fatal { position: fixed; inset: 0; z-index: 50; display: grid; place-items: center; padding: 16px; background: rgba(8, 9, 13, 0.94); }
#fatal .card { max-width: 560px; padding: 24px 28px; background: #151925; border: 1px solid rgba(255, 143, 143, 0.4); border-radius: 14px; }
#fatal h2 { margin: 0 0 8px; color: var(--danger); font-size: 18px; }
#fatal p { margin: 0 0 12px; }
#fatal pre { margin: 0; max-height: 30vh; overflow: auto; padding: 10px; background: #0d1018; border-radius: 8px; color: var(--muted); font-size: 12px; white-space: pre-wrap; }

.noscript { position: fixed; inset: 0; display: grid; place-items: center; margin: 0; }

/* ---- narrow screens: one bottom toolbar, panels as bottom sheets, transport above the toolbar ---- */
@media (max-width: 720px) {
  /* --transport-h: the wrapped transport bar (two rows at phone width); sheets end above it so they never cover it. */
  :root { --toolbar: 56px; --top: 64px; --transport-h: 108px; }
  .rail {
    top: auto; bottom: max(8px, env(safe-area-inset-bottom, 0px)); width: auto; height: var(--toolbar); max-height: none;
    flex-direction: row; align-items: center; padding: 4px 6px; border-radius: 16px;
  }
  .rail-left { left: max(8px, env(safe-area-inset-left, 0px)); right: 50%; margin-right: 3px; justify-content: space-around; }
  .rail-right { right: max(8px, env(safe-area-inset-right, 0px)); left: 50%; margin-left: 3px; justify-content: space-around; }
  .rail-gap { display: none; }
  .transport-bar {
    bottom: calc(max(8px, env(safe-area-inset-bottom, 0px)) + var(--toolbar) + 8px); left: 8px; right: 8px; transform: none;
    max-width: none; flex-wrap: wrap; justify-content: center; gap: 6px;
  }
  .transport-bar #btn-play { min-width: 76px; }
  .bar-sep, .transport-bar .row-label { display: none; } /* "Speed" still names the speed buttons (aria-labelledby) */
  .view-tools { bottom: calc(max(8px, env(safe-area-inset-bottom, 0px)) + var(--toolbar) + var(--transport-h) + 16px); right: 8px; }
  .panel[data-side="left"], .panel[data-side="right"] {
    left: 8px; right: 8px; width: auto; top: auto;
    bottom: calc(max(8px, env(safe-area-inset-bottom, 0px)) + var(--toolbar) + var(--transport-h) + 16px);
    max-height: calc(100% - var(--top) - var(--toolbar) - var(--transport-h) - 32px); z-index: 5; border-radius: 16px;
  }
  .tour[data-modal="false"] .tour-card { left: 8px; right: 8px; width: auto; top: var(--top); max-height: 34vh; padding: 14px 16px; }
  /* While a docked tour step shows at the top, a sheet ends below it, so the step and the control it talks about both show. */
  body:has(.tour[data-modal="false"]:not([hidden])) .panel {
    max-height: calc(100% - var(--top) - 34vh - var(--toolbar) - var(--transport-h) - 40px);
  }
  .chip-gen { display: none; }
}

@media (prefers-reduced-motion: no-preference) {
  .spot { animation: spot 1.8s ease-in-out infinite; }
  @keyframes spot { 50% { outline-color: rgba(63, 214, 200, 0.35); } }
}
@media (prefers-reduced-motion: reduce) {
  .btn, .seg-btn { transition: none; }
}