Colossatron is a weird thing. I'm almost tempted to say that it's barely a game because of the limited input you have on it. You don't control the main character - a giant robot dragon rampaging around cities - but you rather work to improve it by adding weapons on it and by sometimes using one of two skills you can unlock after destroying the first capital. I've had some fun with it, altough it was mostly mindless and I never felt challenged at all by any of it.
First of all, the game isn't very informative about what you should know. I suspect that if Colossatron gets destroyed, you lose a level, but there's no health meter anywhere for the best. All the weapons that you attach break down as they get hit and after a while they are destroyed, but what about the main guy that has to stay alive? I took a skill to make him regenerate over time, what did it actually do? I never actually lost, so maybe you're invincible? I strongly doubt that. There is also way too much stuff on screen - enough to bog down my framerate to single digits on an iPad 3 - to let you plan any strategy or think about any plan, it's too chaotic for that, you're just going with the flow.
I like the multiple choices of weapons per color - there are 3 basic weapon colors, and you can combine the primary colors to make other weapon types - that change every 24 hours and allow you to unlock them by spending some premium currency. This type of currency is distributed fairly regularly, you get some at the end of worlds, you find some in boxes, it's enough to buy a few things you want. You can upgrade the life of your weapons or unlock them, you can also turn premium currency into normal cash. The cash is used between maps to add weapons to Colossatron, repair everything or let you swap the order of your guns around. The guns are fine, homing missiles, life-draining beams, icicle shots, drones, flamethrowers, there is a bit of nice customization here.
That being said, the enemies never change - and if they change, it's not noticeable at all - and the voice clips start repeating pretty quickly. The perks you get after completing worlds are interesting, but I'm not a fan of the fact that you need to spend premium currency to reset them, it's difficult to try different things if there's such a hefty cost associated. When you complete the game, you can 'prestige' to start over with tougher enemies. That might be appealing for some, but I'm done with Colossatron.