Some cards will be unable to cast if conditions are not met such as cards targeting minions when there are no minions on the field, but other cards will cast when only half of the conditions are met without giving the player the ability to stop the cast which is inconsistent and likely not intended. For example, if you cast a spell or a minion that targets something you can put it back in hand if you cancel the targeting, but if you cast a spell that has one legal target but not the second half, it will just cast and fizzle. Warlock Consumption spell for instance. If you have only one creature on the board and the enemy has none, even so much as an accidental tap will cause it to cast and since there are no legal enemy targets it will simply take your mana. I’m sure this happens with other spells as well. Spells with multi-target effects are also inconsistent because they cannot be canceled once the first target is set which is counter-intuitive since there’s no logical difference between targeting nothing and returning the spell to hand and targeting 1 out of x targets and returning it to hand: in both cases the spell or ability won’t resolve if canceled so canceling it after targeting 1 thing and forcing the player to spend mana doesn’t make sense. Canceling at the start or in the middle is functionally the same and this seems like an error with the way these spells are handled in the game.