[Feature] Mental Rotation Blocked CAT

[CCuskley]

We want to move mental rotation wo a within-block CAT. Starting with animals, if theta >x, move to polygons. If theta<=x, stay with more animals. Similar logic at the polygon stage: if if theta>y, move to 3D shapes, if theta <=y, stay with. more polyons.

Additional notes/questions @mcfrank @mikabr

• For now, leaving off the possibility of "levelling down" from polygons back to animals (we want to build in level-down logic for a few tasks, but dont have thresholds for this yet)
• We don't have parameters for polygons; how to proceed?