My partner and I are only about 6:30 hours into the mini dare and we have quite a bit done.

We have a player entity that is controlled by the arrow keys.
Two passive mobs, a pacer that walks between two defined points and a follower that will follow the player if he gets close.
An item-goal (for lack of a better term) that is the core of the puzzle mode. It can block your path until you have specific items and it can give you items. It can activate on collision or on action button.
A one way block that only lets the player move though in one direction.

The next step is building some levels and maybe making some graphics. If we get time we might even make is scary 😛