$breakpoint: 900px;

:root {
  --color-text: #fff;
  --color-ink: #202124;
  --color-accent: #a63446;
  --color-accent-strong: #7c2130;
  --color-background: #eee;
  --color-focus: #ffd166;
  --border-width: 5px;
  --space-xs: 0.375rem;
  --space-s: 0.75rem;
  --space-m: 1.5rem;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  background: var(--color-background);
  color: var(--color-ink);
  font-family:
    system-ui,
    -apple-system,
    BlinkMacSystemFont,
    'Segoe UI',
    sans-serif;
}

body {
  block-size: 100dvh;
  margin: 0;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  overflow: hidden;
}

img {
  display: block;
  max-inline-size: 100%;
  block-size: auto;
}

:focus {
  outline: none;
}

:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 4px;
}

.site-header {
  display: grid;
  place-items: center;
  position: relative;
  min-inline-size: 5rem;
  background: var(--color-accent);
  color: var(--color-text);
  padding: var(--space-m) var(--space-s);
}

.site-header h1 {
  margin: 0;
  font-size: clamp(1.5rem, 4vmin, 3rem);
  font-weight: 300;
  line-height: 1;
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  white-space: nowrap;
}

.gallery {
  min-width: 0;
  min-height: 100dvh;
  display: grid;
  grid-template-columns: minmax(5rem, 10vmin) minmax(0, 1fr) minmax(
      7rem,
      14vmin
    );
  position: relative;
}

.rail {
  min-height: 0;
  max-height: 100dvh;
  overflow-y: auto;
  overscroll-behavior: contain;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-s);
  padding: var(--space-m) var(--space-s);
  scrollbar-color: var(--color-accent) transparent;
}

.thumbnail {
  display: block;
  flex: 0 0 auto;
  border: var(--border-width) solid var(--color-text);
  background: var(--color-text);
  color: inherit;
  box-shadow: 0 0 0 1px rgb(32 33 36 / 16%);
}

.thumbnail:hover,
.thumbnail.is-selected {
  border-color: var(--color-accent);
}

.thumbnail:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 3px;
  box-shadow:
    0 0 0 6px var(--color-accent-strong),
    0 0 0 1px rgb(32 33 36 / 16%);
}

.thumbnail--portrait {
  inline-size: 8vmin;
}

.thumbnail--landscape {
  inline-size: 12vmin;
}

.thumbnail picture,
.thumbnail img {
  inline-size: 100%;
}

.frame {
  min-width: 0;
  min-height: 0;
  display: grid;
  padding: var(--space-m);
}

.frame-content {
  min-width: 0;
  min-height: 0;
  display: grid;

  // A full-width column gives the figure a definite width to size against, so
  // `100%` below resolves to the real available width (not the image's own,
  // content-collapsed width) even before the photo has loaded.
  grid-template-columns: minmax(0, 1fr);
  align-content: center;
  justify-items: center;
  position: relative;
}

.frame-content.is-loading::after {
  content: '';
  position: absolute;
  inset: 0;
  margin: auto;
  inline-size: 3rem;
  block-size: 3rem;
  border: 4px solid rgb(32 33 36 / 20%);
  border-block-start-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  .frame-content.is-loading::after {
    animation: none;
  }
}

// Holds the next photo's <picture> off-screen so the browser fetches it before
// the slideshow advances. Kept renderable (not display: none) so loading runs.
.frame-preload {
  position: absolute;
  inline-size: 0;
  block-size: 0;
  overflow: hidden;
  pointer-events: none;
}

// Size the framed photo to its final, contained dimensions up front — width is
// capped by the available width (100%) and by the height limit scaled by the
// photo's aspect ratio — so the white frame never grows from a tiny box to the
// photo's size while the image is still loading. --frame-ratio is set per photo.
.frame-figure {
  margin: 0;
  inline-size: min(100%, calc((100dvh - 5rem) * var(--frame-ratio, 1)));
}

.frame-figure picture {
  display: block;
}

.frame-figure img {
  inline-size: 100%;
  block-size: auto;
  max-block-size: calc(100dvh - 5rem);
  border: var(--border-width) solid var(--color-text);
  background: var(--color-text);
  object-fit: contain;
  box-shadow: 0 0 0 1px rgb(32 33 36 / 16%);
}

.slideshow-toggle {
  display: none;
  position: absolute;
  inset-block-start: var(--space-s);
  justify-self: center;
  border: 0;
  border-radius: 4px;
  padding: 0.45rem 0.75rem;
  background: var(--color-accent-strong);
  color: var(--color-text);
  font: inherit;
  font-size: 0.875rem;
  line-height: 1;
  cursor: pointer;
}

.js .slideshow-toggle {
  display: block;
}

.slideshow-toggle:hover {
  background: #5f1724;
}

@media (width < $breakpoint) {
  body {
    grid-template-columns: 1fr;
    grid-template-rows: auto minmax(0, 1fr);
  }

  .site-header {
    padding: var(--space-s);
  }

  .slideshow-toggle {
    inset-block-start: 50%;
    inset-inline: auto var(--space-s);
    transform: translateY(-50%);
  }

  .site-header h1 {
    writing-mode: horizontal-tb;
    transform: none;
    font-size: clamp(1.5rem, 7vw, 2rem);
  }

  .gallery {
    min-height: 0;
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto minmax(0, 1fr) auto;
  }

  .rail {
    max-height: none;
    min-width: 0;
    overflow: auto hidden;
    flex-direction: row;
    justify-content: flex-start;
    padding: var(--space-xs) var(--space-s);
  }

  .rail--portraits {
    grid-row: 1;
  }

  .rail--landscapes {
    grid-row: 3;
  }

  .thumbnail {
    inline-size: auto;
  }

  .thumbnail--portrait img {
    block-size: 12vmin;
    inline-size: auto;
  }

  .thumbnail--landscape img {
    block-size: 8vmin;
    inline-size: auto;
  }

  .frame {
    grid-row: 2;
    padding: var(--space-s);
  }

  .frame-figure {
    inline-size: min(100%, calc((100dvh - 12rem) * var(--frame-ratio, 1)));
  }

  .frame-figure img {
    max-block-size: calc(100dvh - 12rem);
  }
}