/* LabLife — equation curtain (formulas, symbols, figures). */
.backdrop {
  position: fixed; inset: 0; z-index: 40; background: var(--backdrop);
  opacity: 0; visibility: hidden; transition: opacity .3s ease, visibility 0s linear .3s;
}
.backdrop.open { opacity: 1; visibility: visible; transition: opacity .3s ease, visibility 0s; }
.curtain {
  position: fixed; left: 0; right: 0; top: 0; z-index: 50;
  max-height: 88vh; max-height: 88dvh;
  display: grid; grid-template-rows: auto minmax(0, 1fr) auto;
  background: var(--raised); color: var(--ink);
  border-radius: 0 0 22px 22px;
  border-bottom: 1px solid rgb(176 105 247 / 35%);
  box-shadow: 0 18px 60px rgb(0 0 0 / 60%), 0 8px 40px rgb(142 69 220 / 18%);
  padding-top: env(safe-area-inset-top, 0px);
  transform: translateY(-104%); visibility: hidden;
  transition: transform .38s cubic-bezier(.2, .8, .2, 1), visibility 0s linear .38s;
}
.curtain.open { transform: none; visibility: visible; transition: transform .38s cubic-bezier(.2, .8, .2, 1), visibility 0s; }
.curtain-head .wrap { max-width: 760px; display: flex; align-items: center; justify-content: space-between; gap: 12px; min-height: 60px; border-bottom: 1px solid var(--line); }
.curtain-head h2 { font-size: 18px; font-weight: 600; }
.curtain-head .eyebrow { display: block; font-family: var(--font-display); font-size: 12px; font-weight: 500; text-transform: uppercase; letter-spacing: 0.16em; color: var(--accent); }
.icon-btn {
  width: 44px; height: 44px; display: grid; place-items: center; flex: none;
  border-radius: 50%; border: 1px solid var(--line-2); background: rgb(255 255 255 / 3%); color: var(--ink);
}
.icon-btn:hover { border-color: rgb(176 105 247 / 70%); }
.icon-btn svg { width: 18px; height: 18px; }
.curtain-body { overflow-y: auto; overscroll-behavior: contain; -webkit-overflow-scrolling: touch; }
.curtain-body .wrap { max-width: 760px; padding-block: 18px 8px; display: grid; gap: 22px; }
.curtain-grip { display: grid; place-items: center; padding: 10px 0 12px; border: 0; background: none; width: 100%; color: var(--ink-2); }
.curtain-grip span { width: 44px; height: 5px; border-radius: 999px; background: var(--line); }

.eq-section { display: grid; gap: 10px; }
.eq-section h3 { font-size: 12px; font-weight: 500; text-transform: uppercase; letter-spacing: 0.16em; color: var(--accent); }
.eq {
  display: grid; gap: 6px; padding: 14px 14px 12px;
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm);
}
.eq-name { font-size: 14px; font-weight: 600; }
.eq .math-box { overflow-x: auto; overflow-y: hidden; padding: 4px 0; font-size: 19px; }
.eq .math-box math { margin: 0; }
.eq p { font-size: 13.5px; color: var(--ink-2); }
.legend { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 10px 14px; margin: 0; align-items: baseline; }
.legend dt { font-size: 18px; min-width: 2.2em; color: var(--accent); }
.legend dd { margin: 0; font-size: 14.5px; }
.notes { margin: 0; padding-left: 18px; display: grid; gap: 6px; font-size: 14.5px; }
.notes li::marker { color: var(--accent); }
.figure { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 10px; overflow-x: auto; }
.figure svg { display: block; width: 100%; max-width: 520px; height: auto; margin: 0 auto; }
.figure figcaption { font-size: 13px; color: var(--ink-2); padding: 4px 4px 0; }
.fig-beam { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.6; }
.fig-axis { stroke: var(--ink-2); stroke-width: 1; stroke-dasharray: 4 4; fill: none; }
.fig-guide { stroke: var(--ink-2); stroke-width: 1; stroke-dasharray: 2 3; fill: none; opacity: 0.8; }
.fig-dim { stroke: var(--ink); stroke-width: 1.2; fill: none; }
.fig-lens { fill: var(--surface-2); stroke: var(--ink); stroke-width: 1.4; }
.fig-text { fill: var(--ink); font-family: var(--font-sym); font-style: italic; font-size: 15px; }
.fig-text-up { fill: var(--ink-2); font-family: var(--font-ui); font-size: 12px; }
.fig-pot { fill: none; stroke: var(--ink); stroke-width: 1.4; }
.fig-level { stroke: var(--ink-2); stroke-width: 1; stroke-dasharray: 3 3; opacity: 0.8; }
.fig-level.filled { stroke: var(--accent); stroke-width: 1.8; stroke-dasharray: none; opacity: 1; }
.fig-dot { fill: var(--accent); }
.fig-wave { fill: none; stroke: var(--accent); stroke-width: 1.8; }
.fig-medium { fill: var(--accent-soft); stroke: none; }