A few spoiler strategy/observations:
Go to safe, enter 326 (from "the shiny"(the Shinning) poster). Grab the axe. Go to the hallway. Use the axe against the end of the hallway. Grab the chainsaw. Go to the next hallway. Use the chainsaw on the door at the very end of the hallway. The end.
Haven't figured out how to get the last 3 secret medals, involving dying, yet.
I don't think there really is a way to fail in this game. You can spam all 4 direction keys and still bag the item, without any negative effect to your points. Upgrade and spam. That's all there is to it getting all the medals for it.
some observations - haven't beaten all the levels, yet, for it.:
The game seems hard at first, but once you know that each enemy type seems weak against a certain tower (purple - speed tower, black - tesla tower - blue- acid tower, grey - slow tower, and bombs everything) it becomes a lot easier. Bombs, aside from certain towers, are probably the most important thing in beating the levels. They can destroy up to 3 small, to medium, enemies and kill most large enemies in one hit, with splash damage to the others.
Major glitch for this game. You can use the hint unlimited times, but beware that the hint is not always accurate.
"Tab" works great for this.