A lot of fun, pay to play is optional (and it keeps getting better)(and better!)

This squad shooter/strategy game has sufficient depth of play to keep you coming back. Although theres in-app purchases available, one can advance pretty quickly up thru level 10 or so. The arena play is quirky, as you can be set against someone far below or far above ones own level. The price is right: try this game! And yes, they offered me 75 crystals for a five star review, but thats what its really worth!
P.S. They also have Great customer support, especially after the latest update which destabilized it a bit.
They keep adding features and layers of combat and they have, mercifully, managed to eliminate several issues that kept crashing the game.
What was a casual strategy game has become nicely complex. Strength has its place, but so does cunning. One can beat much stronger opponents with careful moves.
Each update makes it a little better.

This game is worth your time: Get it.

Wigglepa about Scrap Force - RPG Tactics, v1.43