/* Shared lesson controls for the existing introductory lessons. */
:root{--intro-control-min:44px}
button,select,summary,.tlback{min-height:var(--intro-control-min);min-width:var(--intro-control-min)}
.tlback{display:inline-flex;align-items:center}
.rail{position:static}
.intro-stage-menu{margin:12px 0;background:var(--card);border:1px solid var(--border);border-radius:14px;padding:4px 12px}
.intro-stage-menu>summary{display:flex;align-items:center;cursor:pointer;font-weight:700;list-style:none}
.intro-stage-menu>summary::after{content:'＋';margin-left:auto}
.intro-stage-menu[open]>summary::after{content:'−'}
.intro-stage-menu .chips{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));overflow:visible;padding:8px 0 12px}
.intro-stage-menu .chips button{white-space:normal;text-align:left;border-radius:12px}
.chang-hd:focus-visible{outline:3px solid var(--secondary);outline-offset:-4px}

.chang:not(.mo){display:none}