Very nice game, rather easy but gets harder. For me hard levels were 20, 27 and 30. 20 and 27 solved after getting back to them which shows that it sometimes just needs god idea.
Stuck on level 30, found several non valid possibilities but so far not won. From me 5/5
I was scared like hell basically the entire game. And it is just some stupid flash game and only top down not FPS. And still very atmospheric and very nice. From mine point of view 5/5
Some problems along the way but all of them are already addressed so not going to repeat them.
My way to beat lvl. 7: Collect first the energy diamonds, then start building reactors and one by one take the rest of bonuses. Fill the room with reactors. Dig into the chambers with the makers. Block on top of the makers so you will not lose your own creeper. Reactors everywhere. Dig to top, reactors. place block before the place where the creeper will erupt and many repulsors with as short beams as possible still touching the place where the enemy creeper will go through. lot of blasters and missiles around. If time left place even more reactors on top after more digging. Await the apocalypse. Blocks will go boom most likely but they will hold the first wawe together with the repulsors so blasters and missiles will destroy enough of the creeper.
I managed it on fourth try I think.
Perfect difficulty from my perspective. Took me about 15-20 minutes to finish them all, then additional 10-15 minutes to ace the ones I have not aced on the first try. Easy to understand and yet so many possibilities on how to procede and getting stuck on small thing can slower the progress for some time but yet it does not get frustrating, most likely the music helps a lot. For me 5/5
 "Strand"){kind=icon}
 "The Peacekeeper"){kind=icon}
 "Outpost:Haven"){kind=icon}
 "Creeper World 2: Academy"){kind=icon}
 "Coins"){kind=icon}
 "XenoSquad"){kind=icon}
 "Frantic Frigates"){kind=icon}
 "Z-Rox"){kind=icon}
 "Take Something Literally"){kind=icon}
Not a bad completion time! Congrats!