The game sucks.
The more you replay, the more glitched the gameplay becomes. At first play you have relatively balanced difficulty, but each next try, you have more drills on screen at the same. Red Barrell doesn't always work (doesn't always kill enemies). There should also be a way to reduce the length of the alien snake. It's also not convenient to have to click the barrel, there should be some key shortcut. The lack of tutorial or info only adds insult to injury. The green barrel appears way to frequently. It's extremely hard to get 30 score, let alone 50. Alien snake is too slow, and the drills are annoying. He also doesn't seem to have power enough to push some objects. What's the point of "try again" button if it returns you back to menu?
I could go on and on and on, but what's the point? It's not like you're going to fix it.
All in all, the game is painfully imbalanced, and seems to be more of a beta version.