The game is fun and I enjoyed it. I like the retro style it has, plus it's also a good time killer.
Here are some issues I had with the game:
-Hitbox stays the same when going left or right even though the dimensions of the ship change.
-666 enemy mode lags to all hell because of all the credits bursting out of the killed enemies. Maybe find a way to make it so that enemies don't drop credits in this mode in order to lower lag.
-I tried atleast 20+ times to finish 666 enemies mode legitimately, but it's not possible without the best weapon activated.
-No moment of invulnerability between taking damage, not even half a second. This can cause you to drop from 9 to 0 hearts in certain parts of the last 2 levels, which, let's admit, is kind of bs.