There are some custom challenges from my domestic kingdom rush forum, and I wish you guys would
love them.
Basic requirements
(1) You have to perfect the challenge if it's on a campaign mode, which means that you must get no
lives lost.
(2) If you plan to sell towers, you must build the same number of towers (or more) with the total price which
is no lower than the former one afterwards.
(3) You should spend as less money as you can.