The Riftbreaker is pretty good and has a free demo.

shortylickens

No Lifer
Jul 15, 2003
82,854
17,365
136

No full version yet. The demo is short but good.
I recommend playing it once. Should take you between 10 and 25 minutes depending on how awesome you are.
 

JTsyo

Lifer
Nov 18, 2007
11,709
871
126
I saw one of the dev play session and seems to be the right mix of base building/ TD and RPG. It's on my watchlist.