How can I limit the power of someone who can create gravitational spheres?

In my world, similar to our earth, a person has the ability to create gravitational "spheres".

He can:

• modify its location
• vary the force
• move the sphere (once created)
• select what or who is affected by this sphere

For example if he creates a sphere next to an item, he can move it (like telekinesis) or if he is on a skateboard, go up a hill like if he was downhill with a sphere strong enough always in front of him. Even fly?

My question is, how could I limit his power? Apart the progression level his ability gain, like first small sphere, then more powerful ones, what weaknesses would he have?

posted over 8 years ago

lois6b‭

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