Well said Muximus!
For someone who doesn't make your own sounds, you have a good taste for them! I just died over 50 times trying to get passed those damn spikes and that record scratch kept me going back for more! It was the perfect sound for stopping abruptly and restarting the music. I loved the simplicity of the music too, it showed great restraint which i personally struggle with. Correct me if i'm wrong but did the red runner make a noise before coming on screen too?
If you are looking to make your own sounds there are LOADS of great programs out there! I personally like to use my Reaper, cubase or garageband. I'll either experiment with software synths or record raw sounds with a handheld mic and edit them later.
Also there is a free program called Bfxr that allows you to make custom 8-bit sounds!
Great job!