The first
Death Jr. game was a blast because it featured very smooth controls and innovative mechanics coupled with some good fighting action and puzzles.
Science Fair of Doom pulls from the same playbook with similarly strong results. When an experiment goes wrong and all (literally in this case) hell is unleashed in the vicinity of DJ's school, it falls on DJ and Pandora to restore order. Playing Pandora was always fun, but the game now incorporates the team of two in a more central way. At any point during play, Pandora can take over in spectral form to solve problems or overcome platforming obstacles that DJ can't handle. Good team-based gameplay is always fun, but the addition of Pandora's altered state means that she is phasing out of DJ's reality entirely. New platforms and other elements invisible to DJ can be explored by Pandora and will often mean the difference between DJ progressing in the game. Think of something like
Super Paper Mario with the "flip" feature and you get the idea.
Science Fair of Doom retains the mix of weaponry and hand-to-hand combat that we had in the first game. DJ once again uses his scythe with devastating effects on his enemies. The scythe is more than just a weapon, though. It can be swung around like a helicopter blade to help DJ glide between platforms, or snagged on ledges that DJ can pull up on, but not quite reach by jumping. Pandora has a slingshot that captures the souls of different enemies after DJ destroys them. This soul slingshot can be turned on DJ to give him some power back or it can be used to unlock areas of the game by tripping switches.
Several themed areas of the game are unlocked as you progress, and each will free one of your friends. This device is identical to the way the first game played, but doesn't feel stale here. Weapons are unlocked gradually as you work through each level, and you'll find that collecting souls is its own reward. In the end, DJ's main goal is to free his fellow students captured by evil forces after the strange accident at the science fair. If you enjoy the single-player, you can hook up with a friend that owns the game and play two quick mini-games via wireless connection.