@Joshcarr81, You receive daily creds and each day played in succession gives extra creds, like Balloons 5 but it resets 7 days. I have 440 creds, used thousands haven't spent a penny.
105/144 - I agree the push to spend money is annoying, but over all this is a solid game with lots of content. Well selected placement and upgrades are crucial. 4/5
Haven't spent one penny. 13 Levels beat with 3 medals. 13 levels beat with 2 medals. 68 medals all together. So no you do not NEED to invest $$$ to beat the game. You will have to go back and win levels after your army is leveled up.
Good game. Needs reset on upgrade points and game reset.
Just click them.