Collectible Card Game Headquarters

Hello everyone,
i have a very simple question. I'm playing the quest mode in Forge and got the Neck Snap card on my deck.

It's an instant spell that says "Destroy target attacking or blocking creature".

The problem is that i can't play it when it should be played, after the opponent declares attackers or blockers. I tried in every step before and after them and doesn't seem to work either. I have of course the mana to use it and i'm targeting creatures.

Is it a bug? Or i am being a total noob using it (i started played since 2 weeks)?

I'm using Forge 1.5.47-r-1

Thank you in advance!

You probably don't have your phase stops setup correctly. The phase indicators are either green or red, depending on whether or not you will auto pass priority for that step. Things like Upkeep and Draw default to Red because you typically don't need to do anything in them.

If you want to toggle your priority, you can just click on the phase indicator however you want. So in this case, you probably want your own DB blocks step to be toggled green, and either your opponents DA block or DB block to be toggled green. This way you have an opportunity to activate abilities before damage.