MtG refers to a lot of things as Spells, however, in MtG everything that is cast (monster, sorcery, artifact, instant, enchantment and so on) is casting a spell. The cards in Cards Mastery seem to base the magic cards around taking the word Spell and applying it in the way other games use the word spell. For example: Force of Will in Cards Mastery Counters specifically a "spell". While in MtG Force of Will counters, anything. For Force of Will to accurately depict its MtG counterpart it should be able to counter units, items, and spells, but not traps. Same with cards such as Aetherflux reservouir which would trigger on units and items as well.
If this is a fully intentional implementation to limit the cards in this way, then you can ignore this comment, it just stood out to me as it makes a lot of the MtG cards function considerably different than their intent.