z undos, but its buggy
bug fix: reset board count when undoing
bug fix: properly checks winlose conditions after undoing.  there were problems with reseting board item counts
undoing disables timer. undo recorded as action for replays
undo states now keep track of player score
player cannot earn stars if they undo
undo option after player loses
undo aesthetics: do not show stars for level records, grey out score and time, etc.
input handles when ctrl button is held, used for undo and restart