Thank you all for the awesome feedback !
@Densin Yeah, the weapon is aiming left & right because if it was firing straight it would be really underpowered. We tried that :p (and we plan to make a vertical slice of a more complete version of the game !)
@TheLucky Good point here. We need to implement more visual / audio feedback for the player, and make some ennemies react to the shooting impacts. With all of that, it will be even more satisfying for the player ^^
@funisfun8 Thanks ! I'm extremely glad that you enjoyed the game ! I agree with you for the instrumental songs. Lyrics are not my favorite, and we'll try to use less lyrics-based songs for the more advanced version. We also have a lot of ideas about new mechanics, ennemies, weapons, bosses, etc.. :p
Unfortunately, here is our biggest problem : We tried to find a way to let the players use their custom musics, but our game is too BPM dependent (the walls, the ennemies, and the background are always bumping at the perfect timing of the song's BPM); however, games like Audiosurf & Beat Hazard are more approximative about that. They are using some kind of script that detects kicks & snares, and create pickups & obstacles based on the song notes but not at every beat (Audiosurf), or ennemies and approximative glow amplifyer, exactly like the visuals of music videos on youtube, you know (Beat Hazard), but these games are not BPM perfect. In our case, we already tried to use a script like that, but the walls & background were desynchronized, or were bumping at every peak in the audio source (horrible), and it was not precise. It's a really big problem, and after some researches, we realized that creating an algorithm to calculate BPM of custom songs is really complex, and depends of the sampling of the audio source, etc.. ( [look at this](http://mziccard.me/2015/05/28/beats-detection-algorithms-1/) )
For now, we plan to make a version of the game with a lot of tracks (like a Guitar Hero game), and eventually make some kind of big update with custom tracks later ^^ Trust me, it was a really hard decision to make. The other solution was to change the entire game, and we don't want that.
About your 2nd request, we plan to make some "drop multiplier" whenever the song is becoming intense, so the ennemies could be faster, and spawn more :p (also, some new game influencers mechanics are gonna be implemented).
And finally, we already tried to make the bullets of the player follow the beat; it would work if our game has only 1 weapon, but there will be more, so it will be hard to diversify weapons while constrain them to fire on the beat (or a multiplier of the beat), but nothing is definitive right now :p
Thank you again everybody, and sorry for those english mistakes~