Nah don't worry I'm not a hater. 

Mech Arena (like basically any other app/game) accumulates excess data from memory leaks. This data slowly adds up over time. 

My mech arena on my main device used to have 1.70GB of 'user' data. After uninstalling then reinstalling, that number is now 4 times smaller, saving me over a Gigabyte of space.

Keep in mind this will reset custom control layouts. 

While I'm here, I just want to congratulate the developers on being able to make the actual app so tiny, like I can't even put a number here (measured in tens of MB) because every time I check it gets... Smaller?!