my players are about to spend a lengthy time in a mage city/school. I am trying to find interesting side activities for them to participate in and had the idea of a competitive sport like minigame made for spellcasters. turns out i couldn't find many examples because a spellcasting minigame is rather hard, and i need help.

These are the basic ideas i've had, and i know it's somewhat vague and needs work, but that's why i need help:

• Up to 4 players
• 1v1
• 1v1v1
• 2v2
• Each player has 4 spheres on a 20x20 grid.
• Spheres can start anywhere on the player’s side of the grid
• Level of spell gives that sphere that level of charges.
• A sphere uses 1 charge per space moved and maintains charges at end of turn
• Spells can be cast on the field itself to create obstacles, but only through the sphere’s themselves (ex. casting wall of ice will create a wall of ice in the spaces the sphere moves over)
• If a sphere hits an enemy’s sphere it can use it’s charges to reduce the other sphere’s charges.
• If a sphere is reduced to negative 5 charges it breaks
• Ways to win, deliver 20 charges worth of power to the enemy’s side, or destroy all of their spheres.

What about a horse race where the spectators get to influence the race with cantrips? Have your players place bets, start the race, and go round-by round (no damaging cantrips!) using cantrips in fun and creative ways to get your horse to win.

I mean, there's always Quidditch.

 the horse race idea sounds cool, but idk how many cantrips would really be useful for that.

as for quidditch, i feel like the players would be more distracted by the harry potter reference or trying to steal flying brooms.