Try to ignore the green monster that wants to kill you and concentrate instead on the three switches on the wall.

Every time you shoot a switch it changes colour.  Make the switches match the colours marked above them on the wall: black, blue and orange.  When the colours match, the bridge at the top of the screen will slide into the room next door.

The bridge at the bottom of the screen will also move, but for that you need to set the switches to a different pattern of colours.  So try to think of a pattern of three colours that you’ve seen recently.  (Hint: pink, green, pink.)