Sky Force 2014 is a top down shoot'em up that is free to play but has in app purchases that range from $0.99 - $1.99 per item.
Ranked in these QuestionsQuestion Ranking
Pro Looks and sounds good
The game has high quality graphics, beautiful aesthetics and a great soundtrack.
Pro Has a persistent leveling mechanic
Upgrades to the ship carry over to next playthroughs.
Con Convoluted payment model
Time spent on upgrades and replenishing available ships can be reduced by spending stars (in-game currency). Additionally, after 1000 stars have been spent a store opens that allows removing ads, getting more stars and halving upgrade and replenish times for money.