It doesn’t take much time playing Harry Potter: Wizards Unite (Free) to reach one inescapable conclusion: The Spell Energy situation can be worse than any Defence Against the Dark Arts lecture.
Even though it seems like the denizens of the Wizarding World can conjure up spells until the cows come home once they’ve learned enough magic in the books and movies, you definitely can’t say the same in Wizards Unite. Your supply of Spell Energy (indicated in-game by blue lightning bolts) governs most of the important ongoing tasks in the game, including casting spells to defeat Confoundables and participating in Wizarding Challenges in Fortresses. In short, any time you cast a spell, it costs Spell Energy.
This is true even when the spell is unsuccessful, a realization you may already have had when confronting more difficult Confoundables. It’s all well and good that it might take three casts to triumph, because all it means is tracing the glyph again, and perhaps downing a potion to make the likelihood of success greater. But when you also consider that you’re spending a point of Spell Energy every time, that makes the calculus of what it “costs" to win an encounter somewhat different. (Insert your favorite Young Gamora meme here.)
Even this wouldn’t be so bad except that Spell Energy doesn’t regenerate by itself over time, which is a common expectation for lots of mobile games.  Nor, unfortunately, do you even get a courtesy ...