I knew I wanted Nanase to transform in a way to climb to the top of the ceiling, but it took me a bit to sort out how to make that into a real challenge. I feel this counts.
In regard to Nanase's "figure", I cared less about her being accurate to reptiles (she still has hair, after all), and more making this form look distinct. This is also why I made her face look like that, and why I made sure to make her fingers and toes so big (though that also helps sell the whole "can stick to and climb walls" deal).
EDIT: The color blindness is something I came up with for the puzzle, and not anything to do with her being a gecko.