I just noticed that Portal 2 now has a store where you can modify your robot. I like the way Valve monetize their games. They bring out free DLC, expanding older games with updates and offering them either free (TF2) or at a steep discount. Then they encourage you to buy hats and personalise your character! Nothing like some of the other grind to play free games I’ve played elsewhere.
Two games spring to mind, both free Android games. Samurai vs Zombies and Garfield Defense. Both play in exactly the same way even though they are apparently by different developers. I swear they used the one game engine and just swapped out graphics and sound.
In both games you collect coins to purchase power ups but those purchases are fairly pricey and by the time you get to level 10 you’ll need to grind and play the level 4 or 5 times to get enough coins to buy an upgrade to finish the level.
Still, not a bad way to spend a few minutes while waiting for the bus or something but to be honest I’d rather use my phone to read a book!
I almost forgot to mention the iOS version of Plants vs Zombies. It received a few updates recently which added the ability to plant flowers that reward you with silver and gold. I only tried it briefly but soon discovered that you need to use fertilizer or the plants will wilt. Of course you have to use real money to buy the fertilizer. *sigh*