I think the big bertha is bugged, it shows that its max power and lift are greater than the nuclear reactor at max level+30 but it doesnt fire the penguin nearly as high as the reactor does.
Overall it is a good game, old concept but still well done. Though i have noticed it seems you have done your best some advice for making the game more enjoyable follows: !) make it to where you can save and quit anytime so if people need to take a break they don't have to wait till they finish the current dungeon level. 2) Make the loot have more randomized effect instead of having a different item for every different set of stats. 3) Make the tutorial a bit more in depth (such as with telling people about the inventory as many people don't realize it at first). 4) As an aesthetic add names for the enemies. I hope you take my advice and either update the game with these improvement or make a second one including these features.
one thing i found i liked about the game is that it hardly uses the mouse at all witch lets me focus on the combat and not where my mouwse it at all times
 "Learn to Fly 3"){kind=icon}
 "Questopia"){kind=icon}
 "no-one has to die."){kind=icon}
 "Realm of the Mad God"){kind=icon}
 "Epic Battle Fantasy 4"){kind=icon}
 "This is the Only Level 3"){kind=icon}
 "Get Off My Lawn"){kind=icon}
 "Elemental Balance"){kind=icon}
 "Particle Lab"){kind=icon}
 "Interactive Buddy"){kind=icon}
 "Wish Upon a Star"){kind=icon}
 "Gun Mayhem"){kind=icon}
 "Doodle God 2"){kind=icon}
 "Insectonator"){kind=icon}
 "John the Button Three!"){kind=icon}
 "Arcuz - Behind the Dark"){kind=icon}
 "Toss the Turtle"){kind=icon}