Bonk's Adventure, known as PC Genjin (PC原人, PC Caveman) in Japan and B.C. Kid in Europe, is a scrolling platform game developed by Red Company and Atlus and released in 1989 in Japan and 1990 in North America for the PC Engine/TurboGrafx-16. The Japanese title PC Genjin is a play on the system's original name, PC Engine, with later ports and sequels featuring similar puns. The game was ported to the NES and Amiga. The game was re-released for the TurboDuo in 1992 on the 4 in 1 Super CD game CD-ROM.

In Bonk's Adventure players control Bonk, a caveman with a large head. Bonk's main form of attack is to use his large head to headbutt enemies in close range, juggling them in the air. The player can also headbutt an airborne enemy from below by simply jumping, allowing to constantly juggle enemies for extra points. Pressing the attack button while in the air makes Bonk dive headfirst into the ground and hit any enemy below, while pressing the button again cancels the attack; by continuously mashing the button Bonk will slowly glide, a trick which can be used to reach farther platforms. Bonk can also climb up walls and waterfalls, grabbing them by his teeth and climbing them up as the player mashes the jump button.

By defeating enemies the player can collect smiley faces which are totaled at the end of each world, granting the player extra lives. Players can also find food and heart items to restore health, as well as pieces of meat which power him up. When powered up, Bonk can instantly freeze all enemies on the screen by smashing the ground, while powering him up a second time will make him temporarily invincible. The powered-up forms wear down with time, with Bonk also depowering if hit by an enemy.