When an opponent casts Emergent Ultimatum, the window has me to select 1 card to deny casting. As one be strongly conscious of 2 cards with "opponent casts and I will not lose immediately", the window sometimes prompts mistake.
It will be better if Emergent Ultimatmu have me to separate "2 cards to allow casting" and "1 card to deny casting", similarly to Atris, Oracle of Half-Truths.