Gates of Mansoul (Good)
|Play for free!|
Platform: Brower, PC download
Publisher: Christian Game Developers, 2015
Your units consist of shepherds, evangelists, and such. You earn crystals for defeating each enemy and can then spend those crystals to add more units to your board or purchase upgrades between levels. While it's not the most advanced tower defense game I've seen, it's still challenging enough to be fun. Plus, it's free!