Eh, I'm sorry, but there were just too many bugs in this, and I thought the first music really clashed with the environment... It was so loud, too. I never even realized there was another song following that one, since I switched the sound off at some point. And I
like Explosions in the Sky, so I kept trying to get the music back on every few screens to see if I finally reached an area where their song is playing!
Why would you put two songs into one file? You could use two files and thus finetune which song you want for a particular environment...
There were also some common first level mistakes, such as enemies placed too close to the margin of the screen, becoming unpleasant surprises for anyone approaching them from the adjacent screen; overreliance on enemies and traps appearing when the player approaches, making the player want to go through the level using walk mode only, random illogical no-climb walls that would've been better realized as something else impeding the player's progress. Those are all usual mistakes, but coupled with those bugs they made the level a bit annoying at times...
On the plus side, there were many different environments and even nice extra screens that weren't part of the main story. I liked that, it's always good to see such things. So I hope you'll make more levels, just try to beta test a bit more next time to weed out those bugs