So, this just came up at today's session of Serpent's Skull. If you cast Reverse Gravity as a 10-by-10 ft. square and then use the rest of the spell's area to extend it upwards, what happens if a creature that takes a 15-by-15 ft. square sized area on the battlemap steps onto the Reverse Gravity field? Will it fall or stay on the ground or something completely different?