Arrow keys move the selected gear 1 mm and snap it into mesh; hold Shift for 10 mm or Alt for 0.1 mm. With no gear selected, arrow keys pan. Plus and minus zoom, 0 zooms to fit. Delete deletes the selected gear, Escape deselects it.
Scroll zoomDrag background to panDrag a gear to move and snapDel removeEsc deselectpinch = zoom · drag empty space = pan · drag gear = move + snap · × in the list = delete