The kind of code an idiot would put on their luggage.

R’amen.

I’ve best heard it described as “a rogue and a bard who can only seem to roll Nat 20s and Nat 1s”.

You just described the original Jak trilogy.

What I mean is that remembering stuff (like what someone casting a fireball looks like) is what 3rd edition would call a Free Action, like talking. You can do it as much as you like (that can reasonably fit into six seconds) at any time during the turn, and it doesn’t take up any resources (like your reaction). Even though you’re rolling a check, it isn’t using part of your turn.

If it did take a reaction to identify a spell as it’s being cast, that would mean that remembering something would take the same about of time and energy as an opportunity attack.

Recalling information never requires an action, the check is just there to determine if you know something or not.

If the spell is on a pc’s class’s spell list and it has components (verbal, somatic, or material), they know if the spell is being cast (e.g. if the wizard sees someone casting Fireball, they recognize it from the arm movements, magic words, and the smell of guano and sulfur). If it isn’t, giving the player a DC (10 + level of the spell) Intelligence (Arcana) check to identify it would also be fair.

Oh cool, Wargroove is getting a sequel. Love me some medieval fantasy Advance Wars.