You can now create doors (which creates a new room).
Only one door per person per area, and the only areas allowed for now are outside and underground.
Doors can only be placed if surrounded by background tiles (at least 3x3 tiles).

Use this block pattern in the MakerMeow to create a door:
RRD
RRD
RRD

R = red, D = dirt

The rooms are currently not very customizable but that will improve in the next update.