/**
 * Native-app ENVIRONMENT only — viewport, safe-area, scroll containment,
 * keyboard-awareness, bottom-sheet mechanics, touch behavior. No color,
 * type, spacing-scale, or brand tokens here on purpose: that's the
 * project's own design system (frontend/guide/tokens/), layered on top of
 * this shell per-screen. Every selector below is about *how the app
 * behaves as a native surface*, not what it looks like.
 */

:root {
  /* Safe-area insets, with a 0px fallback for browsers/devices without a
     notch/gesture-bar — env() with no matching hardware just resolves to 0. */
  --app-safe-top: env(safe-area-inset-top, 0px);
  --app-safe-right: env(safe-area-inset-right, 0px);
  --app-safe-bottom: env(safe-area-inset-bottom, 0px);
  --app-safe-left: env(safe-area-inset-left, 0px);

  /* 100dvh accounts for mobile browser chrome (address bar) showing/hiding;
     100vh does not and causes content to jump/clip on scroll in-browser.
     The JS fallback (--app-vh, set in app-shell.js) covers browsers that
     don't support dvh at all. */
  --app-height: 100dvh;

  /* --- 20:9 viewport system (standardized aspect ratio) ---
     MusicLinkd standardizes app screens around a 20:9 aspect ratio
     (reference frame 390×844 / 360×800), while gracefully supporting
     19.5:9 through 20:9 devices. We do NOT force an exact pixel height —
     .app-root fills 100dvh edge-to-edge and the *actual* viewport plus
     safe-area insets define the usable area, so every phone in that range
     renders naturally.

     Practical UI-safe-area values per the 20:9 reference frame:
       Top status/notification area   ~24px (Android) / ~59px (iPhone)
       Bottom system/nav area         ~24–48px (Android) / ~34px (iPhone)
       App content area               between the two
     These land automatically via env(safe-area-inset-*) where the OS
     reports real insets; the fallbacks below keep a floor for browsers
     that don't report them.

     For chrome that sits OUTSIDE the app content but must respect the
     notches/gesture bar, use:
       top bar:    calc(var(--app-safe-top) + var(--app-top-inset))
       bottom bar: calc(var(--app-safe-bottom) + var(--app-bottom-inset))

     Reference tokens (kept as documentation + usable in the workbench):
       --app-aspect: ideal aspect ratio for mockup/preview frames
       --app-top-inset / --app-bottom-inset: min chrome offsets (px)     */
  --app-aspect: 20 / 9;
  --app-top-inset: 24px;
  --app-bottom-inset: 24px;
}

* {
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

html,
body {
  height: 100%;
  margin: 0;
  overscroll-behavior: none; /* kills the native pull-to-refresh/bounce so it feels like an app, not a webpage */
  overflow: hidden;
}

body {
  touch-action: manipulation; /* removes the ~300ms tap delay */
}

/**
 * The single fixed app surface. One per screen. Nothing outside this
 * scrolls; content that needs scrolling opts in via .app-content--scroll.
 */
.app-root {
  position: fixed;
  inset: 0;
  height: var(--app-height, var(--app-vh, 100vh));
  width: 100%;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.app-topbar {
  flex: 0 0 auto;
  padding-top: var(--app-safe-top);
  padding-left: var(--app-safe-left);
  padding-right: var(--app-safe-right);
}

.app-content {
  flex: 1 1 auto;
  min-height: 0; /* required for flex children to actually respect overflow instead of pushing the layout */
  overflow: hidden;
  padding-left: var(--app-safe-left);
  padding-right: var(--app-safe-right);
}

.app-content--scroll {
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain; /* lets this region scroll without triggering the page-level bounce */
}

.app-bottombar {
  flex: 0 0 auto;
  padding-bottom: var(--app-safe-bottom);
  padding-left: var(--app-safe-left);
  padding-right: var(--app-safe-right);
}

/* Toggled by app-shell.js via the VisualViewport API when the on-screen
   keyboard opens, so a focused input/bottom-sheet stays above it instead
   of being covered — the #1 thing that makes a web form feel non-native. */
.app-root.is-keyboard-open .app-bottombar {
  display: none;
}
.app-root.is-keyboard-open .app-content {
  padding-bottom: 0;
}

/* --- Bottom sheet primitive: structural/motion only --- */
.sheet-scrim {
  position: fixed;
  inset: 0;
  opacity: 0;
  pointer-events: none;
  transition: opacity 200ms ease;
  z-index: 40;
}
.sheet-scrim.is-open {
  opacity: 1;
  pointer-events: auto;
}

.sheet {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  transform: translateY(100%);
  transition: transform 280ms cubic-bezier(0.32, 0.72, 0, 1);
  padding-bottom: var(--app-safe-bottom);
  z-index: 50;
  max-height: 90%;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}
.sheet.is-open {
  transform: translateY(0);
}

/* Reduced-motion respect — required for anything claiming "native-feeling transitions" */
@media (prefers-reduced-motion: reduce) {
  .sheet,
  .sheet-scrim {
    transition-duration: 1ms;
  }
}

/* --- Dev-only overlay: flow/screen/state identifiers. Deliberately styled
   minimally and neutrally (not part of the app's visual design) — strip
   this whole block, or the element it targets, before a real design pass. --- */