Thanks for playing. The feedback is very helpful as I continue to work on the game post Jam. I hear you on controls and plan to add full key customization and gamepad support. Gamepad is a must for me too for this style of game.
Re the power cells (green dots) that you can't reach, you do have a jetpack in your inventory (Q to toggle through inventory items, E to use them -- there are bugs here...). Currently the dots aren't used for anything besides score. There are plenty more on later levels.
Re understanding how to get to next room, I gather you are suggesting I add some sort of prompt to press up (W) to enter the door.
Re level gen, loads more is coming here.
Re art, full credit to the original artist for the sprites. I loved the look and only made very small tweaks to get them to work in the context of the game. The trick will be animating them. Hmmm... Maybe he's up for a commission.