It was a PC game and must be 20 or more years old. It was a 2D game where you controlled a dude and had to navigate a level full of monsters and traps, probably to get to some exit. I think all the levels were just on one screen (no scrolling) but I might be mistaken. I have a feeling there was a possibility to have jetpack in the game and fly around the level, but not 100% sure about that. What I do remember though was the ability to create my own levels which I did all the time and then let my brother play it. Anyone knows what the game is called?