You are playing Cube Tank Arena
Cube Tank Arena is a 3D Tank shooting game where you must fight and destroy waves of other tanks in order to get to the next level. At the end of each level is a super powerful boss that you must fight also. Once an enemy tank is destroyed it might drop poer-ups you can use within the game or coins that you can collect and use to buy upgrades for your tank. There are 5 arenas in total to fight in.