Thanks for your feedback! I watched your whole playthrough and was excited to see how someone besides myself reacts to the different situations in the different levels. I wanted to address some comments you had regarding the game:
Random Generation - This doesn't kick in until level 5, and isn't in full force until levels 6~11. The level layout itself (wall placement, crate placement, enemy placement) is static, but what wall, crate, and enemy to place is random. Once you get above level 5, nearly every enemy and crate you encounter is chosen from a random pool. The enemies are always in the same location, but their weapon type is different every time. Some walls may become doors and make certain levels easier. There was a room in level 10 you played through that had to be cleared, but if the level generates correctly, that room becomes optional. It was too hard to implement a full dungeon generator within my time, so I tried to make it as varied as possible given my constraints.
Cooler Health - I agree that it is much too high. It should be at least 25% lower, probably more like 50%. I personally save my flamethrower ammo for quick cooler destruction.
Taking damage after you win - This is actually intended. I thought it would be really funny to see your tank get utterly destroyed by the final enemies after you win each level. You won't lose or have to restart if you win and then your tank takes damage and dies before you hit the next level button. You just get to watch waves of destruction roll over your battered corpse. :)
Speed - This is the speed of your tank, not your firing rate. The reason you didn't seem faster is because a speed increase of 2 (which is what each speed upgrade gives you) is pretty much undetectable on its own. By the end of your run, you had a speed over 120, which is the speed of the mobile bombs, the fastest enemy in the game. The reason your gun seemed faster was because you could tank hits from minigun tanks without dying, which is because the max heat upgrades were upgrading your heat tolerance. You were approaching max heat 200 at the end of your run.
NICE TRY - Yes, that is the secret level. ;)
Again, thanks for the kind words. :)