I think there should be some more tanks

There should be some kind of campaign in the game that way you don't always have to play against other people.

Tankionline is a free online multiplayer game where you can rise up and destroy your opponents. Save crystals to buy new and better tanks and weapons to do event better at the game. You can play on three different modes, free for all, capture the flag, and team deathmatch. You can play on more maps the more you level up. to play this epic game just go to http://tankionline.com.

I think you should be able to sell equipment like weapons, tanks, camouflage, ect. for crystals. The value should vary depending on how many times the item has been upgrade.