OpHog is one of the most interesting and engaging tower defense game developed. The game lets you place defending units in order to defeat the enemy boss of each level while defending your portals.

How to play
In OpHog, you place units in order to defeat the enemy boss of each world while defending your portals. You can buy items in the shop with your diamonds, then use your inventory to equip them to your units or use them.

Some keyboard shortcuts:

I - open inventory
Y - open shop
R (in-world only) - place all unplaced units
Left/right - choose different unit (then press spacebar to buy or place)
Up/down - choose different spawner