A word of warning - if you have a PC and a controller, Downwell is much better with the precision you get with a controller, and also with the extra screen space you have when the virtual buttons don't take up a chunk of the screen, seeing as how you're falling down and the more you can see at the bottom of the screen, the better. It's still a decent game on touch but really shines with a controller on Steam
On the other hand, 80 Days is also on Steam but is absolutely fantastic with touch and fits iOS really well (not played the PC version so can't compare in this case). I'd go with that if it tickles your fancy, and you're interested in the best versions of these games.
I did not like Galactic Keep myself. Felt after a short while that leveling was too slow and my character wasn't progressing. It felt like there was nothing I could really do to get stronger.