Elite interceptor has a prepared spell whose rules text states you may tap or untap target creature. This means you can tap or untap the target regardless of its starting state. It’s perfectly valid to untap an untapped creature, or tap a tapped one.

The way arena implements this spell is a single button that says “take action” or “decline”. When a user takes the action, the client will only “untap tapped creature, or tap untapped creature”. This is not the same as the cast spell, and it actually very confusing.

I had an instance where in response to this spell being cast, my opponent tapped the creature I was targeting to crew a vehicle. I then accepted action because I thought nothing would happen, but the client untapped the creature. This was not expected.

Instead, the client really should present a button to untap the creature, a button to tap the creature, or a button to decline. This makes the spell work like the rules text, and makes the behavior obvious to the user.