First when I booted the game, my fingers went straight for the cursor keys (you know, the arrow keys and such), and to my dissappointment this is hardcoded to WASD. Also, I was unable to find the key that shoots (now that I think of it, might as well be a mouse... not that there would be mouse based aiming). Also, goes without saying that AZERTY keyboards are unusable with this game

So how about:
-A tutorial telling you the keys (like floating boxes with text)
-A possibility of changing said games...
-...or adding the same hard coding to the cursor keys and say X (jump) and C (pew)

Also, I'd like to point out that when the first PC platformers emerged, the cursor keys were the aboslute default for movement, and that was the case until mouse became the tool of aiming in Quake, after which WASD was slowly adapted due to it being more ergonomic way to set your fingers (although truly ESDF is more ergonomic if you think of it). This I know because I lived, and played at that exact era.
Further on the history of movement in games, apparently according to research done by a youtube called Larry Bundy Jr. (Guru Larry) the reason arcades and fight sticks are modified with the movement on the left hand side, is that it is harder to contrtol the game with the movement being on your non dominant hand, that for most people is the left hand. So it is more intuitive for the player to use the cursor keys when the mouse is not needed.

[EDIT]: Came to me that people know Larry better by the Guru Larry, so I added that in.