Very nice
Reminds me a little bit of Redder. You should look in that direction for a little more weirdeness. The gameplay is fine but THERE IS A MAJOR PROBLEM : bullets are going throught the black door so you dont need the 24 or so, black diamonds to destroy the gate keeper in the sky. Once you correct that the only thing is to add a little more to the scenario. I'd suggest something like " the more monsters you kill, the more you become yourself a black monster. That would be what's giving you abilities (instead of randomely finding gear on an unknown planet). And then you could make something like : when you go further, you start finding old, abandoned ships and you start understanding that every black monster is just someone who has been sent here just like you. So you have to kill the boss before it transforms you completely. Hope I helped you and gave you some ideas. Keep up the good work !