I really tried to setup everything, but ran into 3 - 4 different bugs while trying to get into the game. Was really frustrating. The arena menu just stayed open for a while and I couldn't move it so it stayed there until I closed it by clicking on one of the menus. The UX is not intuitive and very confusing. I don't think you need the Buy and Inventory parts. You should just display the tank and let the player click on the individual parts. As they click it should prompt "Buy something new" , "Select from ones that you have" . Or even better, just show everything but keep the "Buy" ones hidden unless the player clicks a checkbox to display them.
What do you think of the combat, is it boring?
Maybe it's not a game for me, but wouldn't it be more interesting if the player controlled the tank they built? Seems like you took the most fun part out and let the AI have the fun xD. Also the AI just wobbled around strangely which didn't end up being that fun imho.
A lot of work and passion went into this, that part is clear. You need to decide what exactly is fun for the player in the experienc e you are building. Then make sure that experience is entertaining. Sadly, right now it just feels frustrating :/