Mudwars.io
FullscreenMudwars.io is an entertaining free-for-all io game with tank upgrades! You have to tunnel around the map to farm precious gold ores and gain points. Every time you level up, you can spend a point on one of the many upgrades you have to choose from, including weapon damage, reload speed, etc. Some of your special abilities in Mudwars.io allow you to go invisible and sneak up on your enemies. That could be a really effective strategy. Give it a try :)