}
  });
  ['pointerup','pointercancel','pointerleave'].forEach(ev=>stage.addEventListener(ev,()=>{dragging=false;}));
  stage.addEventListener('wheel',e=>{
    y=Math.min(maxY(),Math.max(0,y+e.deltaY));
    apply();
  },{passive:true});

  // keyboard
  document.addEventListener('keydown',e=>{
    if(script.getAttribute('contenteditable')==='true') return;
    if(e.key===' '){ e.preventDefault(); toggle(); }
    else if(e.key==='ArrowUp'){ e.preventDefault(); nudge(1); }
    else if(e.key==='ArrowDown'){ e.preventDefault(); nudge(-1); }
    else if(e.key==='ArrowRight'){ setSize(fs+4); showBar(); }
    else if(e.key==='ArrowLeft'){ setSize(fs-4); showBar(); }
    else if(e.key.toLowerCase()==='r'){ restart(); }
  });

  window.addEventListener('resize',()=>{
    const ratio=y/maxY();
    requestAnimationFrame(()=>{ y=ratio*maxY(); apply(); });
  });