Tenser's Floating Disk follows you at a distance of 20 feet and can't move around obstacles. What counts as an obstacle? Suppose you are walking down a narrow corridor that turns a corner:
D = disk; W = wizard; * = wall; . = space between wizard and disc; Each space is a 5' square:
********* ********* D...W-> * -> D.* ******* * *******.* * * *.* * * *W*
Does the corner prevent the disk from following you? If so, would it only be possible to get the disk around the corner if you first moved straight for 20', like making a wide turn in a semi truck? If so, it seems rather useless in some circumstances.
Tenser's Floating Disk
This spell creates a circular, horizontal plane of force, 3 feet in diameter and 1 inch thick, that floats 3 feet above the ground in an unoccupied space of your choice that you can see within range. The disk remains for the Duration, and can hold up to 500 pounds. If more weight is placed on it, the spell ends, and everything on the disk falls to the ground. The disk is immobile while you are within 20 feet of it. If you move more than 20 feet away from it, the disk follows you so that it remains within 20 feet of you. It can move across uneven terrain, up or down stairs, slopes and the like, but it can't cross an elevation change of 10 feet or more. For example, the disk can't move across a 10-foot-deep pit, nor could it leave such a pit if it was created at the bottom. If you move more than 100 feet from the disk (typically because it can't move around an obstacle to follow you), the spell ends.