Duo Vikings

Duo Vikings gives its two playable Vikings identical fighting ability but places puzzles that assume two bodies working together, one Viking holding a switch while the other passes through a door it opens, which makes solo play through both characters closer to solving a puzzle twice at once than playing normally.

Levels are built around that split-attention challenge specifically, so switching between characters constantly rather than parking one in a safe spot tends to be necessary rather than optional. Playing with a second person removes the character-switching entirely and turns the same puzzles into genuine coordination challenges, which changes the pacing considerably compared to a single-player run. Castle Pals runs a similar two-character puzzle-platformer format if this dual-character structure is what you enjoyed most.