The game was prehistoric in more ways than one. It had a late 80s technology look to it and the game itself had a prehistoric theme.
It was called Trogman and the player character was a small cartoon caveman who fought dinosaurs with his club. Usually he could only take on smaller dinos but when he found large fossil humanlike footprints he temporarily turned into a huge sasquatch-like being with super strengh, able to take on even the largest dinos like T-rex.
The game was coin operated, but the coin mechanism was missing so Andrew could have a free game. He looked at the door. He didn't look like he was going to be disturbed so he activated the game.
There was a flash and Andrew found himself in a barren, rocky landscape. Looking down at his body, he saw he was slightly shorter, but slightly hairier with a slouched back, apelike brow and big feet. He was also clad in only a fur loincloth and carried a large wooden club.
"I'm Trogman!" he grunted.