In the Boomsday Project solo adventure, the secret lab, clear Dr Boom, level 4 of 4:
Sorcerers apprentice does not reduce the cards to 0
https://gyazo.com/c951c6cb610723205b83e031740e3a84
This picture clearly shows that 2 cost spells remain costing 1, despite 2 sorcerers apprentices. Without the reduction to 0 mana, this puzzle cannot be solved.