who blinks first

Meaning who gives in or backs down first in a confrontation or negotiation. The phrase doesn't refer to the literal act of blinking, but rather to a situation where someone is waiting for the other person to yield or concede.

"We both have an ok trade if we don't do anything, but maybe I want to use this trick to change the outcome, but if I wait you might mess up and cast it first" stalemate situation today after not playing for a bit.

In case someone isn't aware, during combat phase BOTH players can cast their spells at any point. Often it doesn't matter because one player clearly blocked with the intent to use a combat trick, but sometimes it plays out super awkwardly.

For example, Player 1 is attacking with a 2/2 and is blocked by Player 2's 2/2. Both players have Finest hour AND Torch in hands. In this case, both players may want to Finest Hour to win the trade (let's say, they are both low on creatures and need one to finish the game). The issue is that whoever casts Finest Hour first gets blown out by opposing Torch. This means that the optimal play is to wait until the very last second of the combat phase and hope your opponent blinks first. Or simply accept that you never cast your spells in an even trade situation. It's weird.

In a game like Magic (as devs are obviously aware), active player (attacking player) has to pass priority first and then if their opponent passes it back, neither player can cast anything before combat damage happens. So there's a risk involved and one player has the advantage defined by the rules.

I get that devs want to lower the amount of phases in the game, but goddamn, if you played a tourney and people were tryharding, it would be 100% correct to always wait the timer out. Even if it may not be relevant right now, this is just such a big hole design-wise it legitimately annoys me.