I think there's a bug in the game where in the 3rd level you can constantly get a heart from the chest after dying. I don't know if this was intentional or not but i don't think it was

I recorded my entire play session and planned to show it to you, only I didn't realize that by the time I was done, the recorder stopped after ten minutes :( But I did roll credits on the game!

1. Great visual style
2. Solid sound
3. Music fit really well.
4. Difficulty curve was a tad steep, I wish I was able to get more confident with the dash ability before needing to rely on it so early. Even by the time I completed the build, I wasn't 100% confident when using the dash. I couldn't get a firm read on where Boomer would end up, distance wise, whenever I'd use it. This may be on me, though.
5. The horizontal distance of the jump doesn't seem to match the speed at which Boomer is running. The fact that it's very vertical, cutting the distance and speed, felt a bit jarring, but I suppose that's by design and I'd get used to it.
6. I'd recommend adding (not replacing) the ability to float or dash to the L and R triggers. This way, your thumb doesn't have to travel from the opposite side of the face buttons (X to B, or B to X) when needing to be quick. You could always have your thumb on the button you want and simply tap a trigger button. I did this with my game and it's improved the experience a lot IMO.
7. Add a visual cue to the character itself when you're getting low in stamina. Sometimes I'd run out and completely not notice because I didn't want to take my eye off of what I was doing to look in the top left corner of the screen. Perhaps the light that emits from him gets dimmer as his stamina runs out? Or he makes a sound when it's almost out? Some kind of visual/audio cue.
8. I found that I was not able to always double-jump, randomly. This seemed to occur a lot when on crumbling platforms. But other times, I just was not able to double-jump. This also occurred when trying to wall-jump. I'm not sure if it's because I would burst too fast into the side of walls and that's why... but there were numerous times I was expecting to be able to wall-jump, and Boomer would lose grip and I'd die.

Overall, really well done. I love it, already. And I'm pretty picky!

To answer your questions directly:

• How did the movement feel? I liked moving left and right, but the dash mechanic felt a bit too unpredictable.
• Did you play with Keyboard/Mouse or Gamepad? Both.
  • If you tried both, which do you prefer? Gamepad by far. I would never have been able to complete this build using keyboard.
• What would make this experience better? Mentioned above. 
• What would you like to see in the world of Boomer? I'm excited to hear more music and see more visuals. I'd even like to know a bit of the story, if there is any. Are the fragments you collect adding up to some bigger goal/world to unlock?