Thanks a lot for your review and comments!
Here's some notes based on your message:
The visual/audio indicator when damage is received is definitely in our to-do list.
Some people find the controls difficult on their first few games, so we're happy that you managed to make it work on your first game.
We have 7 weapons in the demo. We should have 14 weapons and 11 systems when we release.
The fact that the music was absent is definitely a bug that was introduced in the last week, we're investigating.
We're really glad that you liked it and we hope that you come back to it in the future!