Some campaigns (ok maybe just Midnight 2nd Ed) utilize a spell point system 'Spell Energy' instead of a 'Spells per day' framework. This works very similar to most video game RPGs using a magic point (MP) system where a player can cast known spells as many times as they want until they run out of points. More powerful spells obviously cost more points.
There was a UI request to show how many points a player has available instead of the typical 'Spells per Day' block. Let me know if you need any more information.