Think I know what's happening here! My way of preventing too many keystrokes in quick succession is pretty hacky—basically, if you keypress <300ms after your last physical keypress, it doesn't fire an event. More appropriate would be to only suppress the event if it's <300ms after the last keypress that actually fired an event (vs all keypresses). Will fix ... :P

(The game mechanics should be identical to the iOS app though, with the exception of the occasional high-number tiles provided. Also in my todo list to figure out the algorithm the game uses to generate them, haha.)