Case: You have maximum of 4 plants on the level, you have 3 and can build one more. Clicking to build one when at the same time and even a little after your third plant dies gives you "Max" even thou you have only 3 of them at the moment. It takes some time to realize you have only 3 and unlock "build" button.
Good game. It would be even more if there were button "hold position".
4 buttons for controll entire army and only 2 of them works, wtf? Make only 2 then maybe?