OK. I've been on the game over 2 hours. I have all 4 colors, super pellets & super beams. I haven't been able to get past the blue grav-repellers in several places, nor any locks where the colored machinery is behind a wall.

I'm assuming I missed a weapon somewhere, but I've been back to every level several times and am just not finding it.

Help?

Did you completely explore the Forest? (besides the part you can't go in yet, of course)

Yeah, you've still got quite a bit of the game to go.

Have you found the forest? That's what the green gun opens up to you. You get to it via the factory. I'm pretty sure that's where you need to be.