Thanks for trying out the game 
This was my second game (first was a Pong clone
) so I didn’t make much effort on some important details that you pointed out. Adding some flashes is a really good idea, would make the game a bit more ‘alive’ and indeed would help the players understand what’s going on. Everything else you said I also agree with.
Regarding the ammo count: the thing is that picking up ammunition replaces what ever ammo you already had. Meaning if you had ‘bouncing bomb’ and picked up ‘speed missile’, whatever bouncing bomb ammunition you had would be replaced with speed missiles. Also each weapon grants you a different amount of ammo when you pick it up. For example picking up ‘bouncing bomb’ gives you 4 ammo, but picking up ‘landmine’ gives you 2 ammo. And again whatever you picked up deletes whatever you already had.
It’s not a bug, but it is confusing. Next game I’ll make picked-up ammo add up and not replace the present ammo. And yeah showing the player exactly what kind of weapon he has at any moment is also a good idea.
I will apply these suggestions in my next games
Thanks