Indeed what you hope was right. It was a conscious decision.
At one point the bullets were destroying themselves upon contact and it felt kinda flat. I was debating between making the bullets ignore each other or colliding with each other. I chose the later.
But then as they collided it filled up the screen quickly... so I made them actually get destroyed about a second and a half after they collide.
It felt good.
Starting room being green was actually meant to show that you were outside the dungeon. The game needed more graphics.