It wasn't too difficult (or easy) once you understood what to shoot. That wasn't very clear at the start.
I found the hardest part was getting around the green 'pistons' without falling off the sides. It wasn't clear that they would kill you if you walked on them. I thought they would allow you to jump onto something that was high up.
Sometimes the balloons went under the floor and could still kill you but could not be shot.
When you go into the 'portal' it can obstruct your view of things that are firing at you. Unless my setting is making me too high.