End-of-the-turn casting in Magic Arena

Question

I'm playing Magic Arena after quite a long time away from Magic. I still remember how to play but there's something that's keeping me confused about the priority system.

When I'm passing the turn, eventually the opponent plays an instant speed spell before his turn, and the game does not allow me to respond to it. I didn't remember this rule but still OK (although that make instants and permanent spells with flash much more powerful than I thought they were).

But in my last game I just played an enchantment with flash at the end of my opponent's turn, hoping that my opponent could not answer to it with a counter spell, but they were able to respond and indeed countered it.

I searched for rules of end-of-turn casting and I think that it's just a glitch of the game (it's still on beta and there's some of them), but I'm not sure. Any help will be appreciated.

Answer 1

You can activate full control mode.

MTG arena has policies in place to speed up the gameplay considerably. This auto pass of priority is an attempt to remove the slow gameplay that has plagued MTGO.

You can deactivate this feature temporarily by pressing CTRL, you can turn it off permanently by pressing CTRL + SHIFT. Take note that when I say permanently, I mean for that game only; it will revert back to the default of setting when you start a new game.

Read more here.

Answer 2

Each player gets priority before each object on the stack resolves, so you can respond to (almost) every action your opponent takes.

Sometimes you will auto-pass priority in Arena though. Arena will auto-pass priority if you have no actions you can take (i.e. if you have no instants in hand or don't have enough available mana to cast a spell or activate an ability) or if you've hit the bottom end turn button. You can enter "full control" mode (I think it's the ctrl key to toggle it) and you will received priority even if there are no possible actions you can take. You can also toggle the "end turn" button off to stop passing priority if you've previously clicked it and have something you can do.

Answer 3

A spell resolves when all players pass priority.

608.1. Each time all players pass in succession, the spell or ability on top of the stack resolves.

This is the only time a spell resolves, so one can always respond to a spell before it resolves.

...Except, of course, if you are unable to cast a spell.

702.60a Split second is a static ability that functions only while the spell with split second is on the stack. “Split second” means “As long as this spell is on the stack, players can’t cast other spells or activate abilities that aren’t mana abilities.”