-  - Select/Cancel Rain of Fire spell.
-  - Select/Cancel Reinforcements spell.
-  - Select/Cancel Hero
-  - Select/Cancel Extra Hero
- Space - Cancel any selected spell/power/rally point.
- P - Pauses the game.
The sequel of Kingdom Rush. It has the same thought. Defend your Kingdom, because it is under attack. The difference between Kingdom Rush and Kingdom Rush: Frontiers is that in Kingdom:Frontiers you have more maps, more options, heroes are introduced, dynamic maps, skill points for heroes, new types of soldiers and so on. There are a lot of other features, in fact almost every single aspect of the game gained new features.
If you already fall in love with Kingdom Rush, then you should definitively play this one as well. It has again a big addicting factor and as soon you start you will be attached to the game.
If you have not played Kingdom Rush, you should play it as well!