The more I do walk cycles, the more I see how feet work. They are actually passing the floor from one to the other! 

Same as a climber who grabs a rock and pulls it down.

Now I’m trying to learn how to do walk cycles in 3d, like walking toward the camera or away. One lesson I learned from Ivvy’s animation was to keep the character’s body the same colour - this way the animation can imply 3d without actually drawing perfect perspective