Mudwars.io is a fun free io game with tank upgrades!
Play game Mudwars io:
You have to dig a tunnel around the map to raise valuable gold ore and earn points. Every time you level up, you can reserve a point for one of the many upgrades you have to choose, including weapon damage, reload speed, etc. Some of your special abilities in Mudwars.io allow you to stealth and sneak your enemies. Try the game!