/* Short practice and folded solutions, matching the STAT 8561 pattern. */
div.theorem[id^="exr-rv-"] {
  border-left: 5px solid #34495e;
  padding: 1em 1.2em;
  margin: 1em 0;
  border-radius: 10px;
  background: #fff;
}
div.theorem[id^="exr-rv-"] .theorem-title { color: #34495e; display: block; margin-bottom: .4em; }
details.solution-collapse {
  border-left: 5px solid #16a085;
  background: #f7fcfa;
  padding: 1em 1.2em;
  margin: 1em 0;
  border-radius: 10px;
}
details.solution-collapse > summary { color: #147d68; font-weight: 600; cursor: pointer; }
details.solution-collapse-body { padding-top: .7em; }
@media print { details.solution-collapse > * { display: block; } }

details.rv-optional { margin: 1em 0; padding: .8em 1em; border-left: 4px solid #427d6b; background: #f7fcfa; border-radius: 6px; }
details.rv-optional > summary { font-weight: 600; cursor: pointer; color: #315e50; }