Another Cave-head, I enjoyed the demo (DD64). My impressions seem to be similar to the other comments.
* When I started the hit box wasn't where I expected it (I think I expected it to be closer to the cockpit). Since I'm focusing further up the screen and not recognizing the player ship past being a blob moving around, the hitbox being closer to the top of the blob might help. By the end of the demo I had it figured out.
* Unfocused shot seems to be lacking in density a little (maybe this is just before any power-ups?) There would be times that I fire at flying enemies a bit and they still reach the bottom of the screen, so they require a bit more attention than I'm used to. Later on I realized being higher up the screen and point-blanking everything increases fire rate (because of the on-screen bullet count?) which made the shots and enemies behave as I expected.
* On the tank mini-boss I was firing at it and hitting nothing, turns out there was a cannon or something on the far side I hadn't destroyed. I was confused for a moment before grazing it and noticing it flash red.
And a few minor bug-ish things:
* In the settings screen I opened the prompt to set something, somehow focused away from the dialog, and because the mouse cursor is hidden I couldn't get back in
* In campaign mode, I lost to the main boss and after the restart a few bullets were still on-screen (they drained away before the actual fight started, I didn't try to catch one)
* End of area 17, was that an upside-down wheelchair mark?
Thanks for the demo, I'm looking forward to seeing what comes next.