Two broken things: If you click on a unit with bad timing while the game's thinking about something else you can get the unit selection out of sync with itself, such that when you click on the unit it toggles between showing the unit's movement but saying nothing is selected, and showing no movement but saying 'unit' is selected. In neither state will the unit move. Also, purchasing new units is multiply broken. After purchasing the first unit, an image of the unit is frozen onto that square for all time. You can move the unit away, but an image will always remain on the tower square. Also, purchasing a unit does not seem to actually remove gold from your purse. Between those two things, it would be really hard to know whether you had clicked the button, except for the third way purchasing units is broken: Once you click that button, nothing else works except the end turn button.