/* ==========================================================================
   Niveus — Window
   --------------------------------------------------------------------------
     .nv-window                   a framed application window
     .nv-window--inactive         a window that does not have focus
     .nv-window__titlebar         controls · title · trailing actions
     .nv-window__controls         the three lights, at the start of the bar
     .nv-window__control          one light: --close, --minimize or --zoom
     .nv-window__title            the window's name, centered on the bar
     .nv-window__actions          trailing slot for a few ghost buttons
     .nv-window__body             the content area

   <div class="nv-window">
     <div class="nv-window__titlebar">
       <div class="nv-window__controls">
         <button class="nv-window__control nv-window__control--close" aria-label="Close"></button>
         <button class="nv-window__control nv-window__control--minimize" aria-label="Minimize"></button>
         <button class="nv-window__control nv-window__control--zoom" aria-label="Zoom"></button>
       </div>
       <span class="nv-window__title">Settings</span>
     </div>
     <div class="nv-window__body">…</div>
   </div>

   A window is a solid object: the content it holds never sits on glass. Its
   titlebar is a raised strip lit like a control, and the controls are three
   lights at its start — close, minimize, zoom — always in that order and in
   those colors, because people find them by position and color before they
   read anything. Their glyphs appear only while the pointer is over the
   group. An inactive window greys its lights and steps back one elevation,
   and the lights regain their color the moment they are hovered.
   ========================================================================== */

.nv-window {
  display: flex;
  flex-direction: column;
  min-inline-size: 0;

  background-color: var(--nv-color-surface);
  background-image: var(--nv-sheen-surface);
  color: var(--nv-color-text-primary);
  border: var(--nv-border-width) solid var(--nv-color-border-subtle);
  border-radius: var(--nv-radius-xl);
  box-shadow: var(--nv-highlight-top), var(--nv-outline), var(--nv-elevation-4);

  overflow: hidden;
  transition: var(--nv-transition-surface);
}

.nv-window--inactive {
  box-shadow: var(--nv-highlight-top), var(--nv-outline), var(--nv-elevation-3);
}

/* --- Titlebar ---------------------------------------------------------------
   Three columns with the outer two sharing the slack, so the title stays on
   the window's center line whatever the controls and actions measure. */

.nv-window__titlebar {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--nv-space-3);
  /* Slim, as titlebars on the desktop are: tall enough for the lights and
     a label, not a toolbar's height. */
  min-block-size: calc(var(--nv-control-height-sm) + var(--nv-space-1));
  padding-inline: var(--nv-space-3);

  background-color: var(--nv-color-surface-elevated);
  background-image: var(--nv-sheen-raised);
  border-block-end: var(--nv-border-width) solid var(--nv-color-border-subtle);
  box-shadow: var(--nv-highlight-top);
  user-select: none;
}

.nv-window__title {
  grid-column: 2;
  min-inline-size: 0;
  overflow: hidden;
  font: var(--nv-font-label);
  font-weight: var(--nv-font-weight-semibold);
  color: var(--nv-color-text-primary);
  text-overflow: ellipsis;
  white-space: nowrap;
}

.nv-window--inactive .nv-window__title {
  color: var(--nv-color-text-tertiary);
}

.nv-window__actions {
  grid-column: 3;
  justify-self: end;
  display: flex;
  align-items: center;
  gap: var(--nv-space-1);
}

/* --- Controls ----------------------------------------------------------------- */

.nv-window__controls {
  grid-column: 1;
  justify-self: start;
  display: flex;
  align-items: center;
  gap: var(--nv-space-2);
}

.nv-window__control {
  --_light: var(--nv-color-window-close);
  --_c: var(--_light);

  position: relative;
  flex: none;
  inline-size: var(--nv-space-3);
  block-size: var(--nv-space-3);
  margin: 0;
  padding: 0;

  background-color: var(--_c);
  background-image: var(--nv-sheen-filled);
  border: 0;
  border-radius: var(--nv-radius-full);
  box-shadow: inset 0 0 0 var(--nv-border-width) var(--nv-color-window-control-ring);

  cursor: pointer;
  appearance: none;
  -webkit-tap-highlight-color: transparent;
  transition: var(--nv-transition-colors);
}

.nv-window__control--minimize { --_light: var(--nv-color-window-minimize); }
.nv-window__control--zoom { --_light: var(--nv-color-window-zoom); }

/* The glyph is two bars drawn from the light's center: crossed for close, one
   for minimize, a plus for zoom. They are always present and fade in, so the
   whole group reveals at once instead of one glyph at a time. */
.nv-window__control::before,
.nv-window__control::after {
  content: "";
  position: absolute;
  inset-block-start: 50%;
  inset-inline-start: 50%;
  inline-size: 55%;
  block-size: calc(var(--nv-border-width) * 1.5);
  translate: -50% -50%;
  background-color: var(--nv-color-window-glyph);
  border-radius: var(--nv-radius-full);
  opacity: 0;
  transition: opacity var(--nv-duration-fast) var(--nv-ease-standard);
}

.nv-window__control--close::before { rotate: 45deg; }
.nv-window__control--close::after { rotate: -45deg; }
.nv-window__control--minimize::after { display: none; }
.nv-window__control--zoom::after { rotate: 90deg; }

.nv-window__controls:hover .nv-window__control::before,
.nv-window__controls:hover .nv-window__control::after,
.nv-window__controls:focus-within .nv-window__control::before,
.nv-window__controls:focus-within .nv-window__control::after {
  opacity: 1;
}

.nv-window__control:active {
  background-image: none;
  box-shadow:
    inset 0 0 0 var(--nv-border-width) var(--nv-color-window-control-ring),
    var(--nv-elevation-inset-sm);
}

.nv-window__control:focus-visible {
  outline: none;
  box-shadow:
    inset 0 0 0 var(--nv-border-width) var(--nv-color-window-control-ring),
    var(--nv-focus-ring);
}

.nv-window--inactive .nv-window__control {
  --_c: var(--nv-color-window-inactive);
}

.nv-window--inactive .nv-window__controls:hover .nv-window__control {
  --_c: var(--_light);
}

/* --- Body --------------------------------------------------------------------- */

.nv-window__body {
  flex: 1;
  min-block-size: 0;
  overflow: auto;
}