Needs Improvement
Overall I have to say I enjoyed playing the game. It has a simple concept and it's executed pretty well. That being said, the game is in need of a few improvements.
1) Penguin pathfinding. I've failed several levels not because my penguins weren't strong enough, but because they kept getting stuck behind obstacles for quite a long time. They also sometimes prefer to pursue an enemy across the room instead of right next to them.
2) Money acquisition. It was easy enough to get money, but in later levels, especially the metal levels with such giant stages, it gets hectic very quickly. I'd like to see upgrades to the collection system, such as increased collection radius and attraction speed/strength.
3) Hotkeys. Given that money acquisition is key, and you use your mouse for it, it can be difficult to keep collecting money and use specials. I'd like to see hotkeys for the different specials, like the number keys, to remedy this situation. Similarly, I'd also like to see something like a shift-click option with bombs to keep using them without clicking the bar after every detonation.
All those issues aside, you still have a solid game here. I liked the different upgrades to the penguin army, and I found myself playing for over an hour before I realized how much time had passed. I don't play with sound, so I won't comment on sound effects or the music.
Overall, the game gets a 7/10 from me.