During a GDC postmortem for the classic game, Cerny said that the concept came about because the post-crash game market (and Atari) demanded totally unique concepts with two-player functionality. Two players meant twice as many coins per play, after all. And so Cerny set about with a minigolf-inspired game that used new 3D hardware -- which eventually ended up 2D, with a new "budget" arcade board that used interchangeable cartridges and afforded a bit more storage space.
Cerny gave an abstract look to the game, with enemies like Slinky creatures and transparent blobs (the transparency was simulated by drawing the floor grid onto the enemy sprite). So he was understandably irritated when the cabinet designers decided to make the trackball controller a smiley face. Eventually, they reached a compromise, with a sort of smiling character on the panel, but not quite a face, and not on the trackball itself.
After the year or so of design, Cerny and Atari ended up with a hit -- for about six months. Sales dropped off, he said, because the game could be completed in four minutes. He lamented not spending more time designing levels after getting the tech in place; at eight minutes, it could have remained a hit, he said.