Two things. 1: The battle commands present in the tutorial don't seem to show up in later levels (just annoying, nothing special). 2: Related to 1; if you leave a purchase unit window open (warriors, archers, mages, rogues) you can buy a unit even after the timer runs out.
I hate when you have to buy things in order as opposed to simply going the hard route, saving up all your money, and flearning that you couldn't buy it without wasting money first. Like tier upgrades....if you show us how much money it is then let us buy it, i'd be fine with paying a little extra for skipping level 2 and going right to level 3...not more than paying for levels 2 AND 3 mind you....but a little more....so I have level 1 wall, finally have enough money to buy fully upgraded wall, but it won't let me. Bull Shit! 3/5 because I could play last stand 1 or 2 for damn near experience. Not bad though :P
 "Royal Warfare"){kind=icon}
 "Vanish Rain"){kind=icon}
 "Achievement Unlocked 3"){kind=icon}
 "GemCraft"){kind=icon}
 "Use Boxmen"){kind=icon}
It's an old bug, forgot to remove it )