Simple mechanics, complex combinations. It's like Sudoku met the Theory of Relativity.
The real beauty of this game comes from the fact that you can create your own levels, and it converts your item placement into a code that other players can use to play it. For example, here is a short level made by me, for those wanting an extra challenge after beating the missions:
{!2%"3G#0G$0"%0#(0"+09,0#-2.01010#50$72G80"90";0#z0+?0#@0?A0|C2|D0"I0#J0"K0"L1+M0"O0DS0|T0@W2|X0@Z0"^0$_0"`0"g1Ah2/o2)y0&~,#/.6/,54)/.~!/".#6-65C6075?C@0A5I@J@K9S?T?}
 "Knightmare Tower"){kind=icon}
 "Electric Box 2"){kind=icon}