Levitating entities

How would I go about creating an entity that if you place another entity over it, it will levitate that placed entity.
Any links would be helpful

Sorry guys im drunk and I want to code

  1. learn to make SENTs in general
  2. find the entity (or entities) above your SENT
  3. apply an upward force every tick to negate gravity

You could use an PID Algorithm to keep that Prop Floating!