* { box-sizing: border-box; }
body, html {
  margin: 0; padding: 0; height: 100%;
  display: flex; flex-direction: column;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
  background: #fafafa; color: #111;
}
#topbar {
  background: #333; color: #fff;
  display: flex; gap: 6px; padding: 8px; align-items: center;
  overflow-x: auto; flex-wrap: nowrap;
  scrollbar-gutter: stable;
}
.tab {
  background: #555; color: #fff;
  padding: 6px 14px;
  border: none; border-radius: 4px;
  cursor: pointer; font-size: 1rem;
  display: inline-flex; align-items: center;
  flex: 0 0 auto;
}
.tab:hover { background: #777; }
#container {
  flex: 1; display: flex; min-height: 0;
}
.sidebar {
  width: 13%; background: #eee;
  display: flex; flex-direction: column;
  padding: 8px; overflow: auto;
  border-right: 1px solid #ccc;
  min-width: 160px;
}
.sidebar button {
  margin-bottom: 6px; padding: 6px;
  text-align: left;
  border: 1px solid #bbb; background: #fff;
  cursor: pointer; border-radius: 4px;
  font-size: .85rem; transition: .15s;
}
.sidebar button:hover { background: #e6e6e6; }
#viewer {
  flex: 1; display: flex; align-items: center; justify-content: center;
  overflow: hidden; position: relative; background: transparent; min-height: 0;
}
#viewer embed, #viewer iframe {
  width: 100%; height: 100%; border: none;
  object-fit: contain; display: block; background: #fff;
}
#viewer img {
  max-width: 75%; max-height: 75%;
}
#topbar a.tab {
  text-decoration: none;
}
@media (max-width: 720px) and (orientation: portrait) {
  #container { flex-direction: column; }
  #viewer { order: 0; }
  .sidebar {
    width: 100%; order: 1;
    flex-wrap: wrap;
    gap: 6px 8px; overflow-x: auto; overflow-y: hidden;
    padding: 6px; border-top: 1px solid #ccc;
    max-height: calc(3 * 1.2em + 6px + 6px);
    align-items: flex-start;
  }
  .sidebar button {
    margin: 0; padding: 0 10px;
    white-space: normal;
    flex: 0 0 auto;
    display: flex; flex-direction: column;
    justify-content: center; align-items: center;
    font-size: .85rem; line-height: 1.2em;
    height: calc(3 * 1.2em + 6px);
    text-align: center;
    gap: 1px;
    max-width: 70%;
  }
  #viewer img {
    max-width: 100%; max-height: 100%;
  }
}