If you've been playing Legends of Runeterra for a while, you may have noticed a few changes with the order abilities and spells activate. Starting with patch 3.6, "cast" cards activate when you "play" them.
But what does this mean? Let's first define cast and play.
What it means to play a card: when a card leaves your hand into play or onto the stack, that’s “Playing” a card.
Casting is a little different - A card is cast once its ability is activated.
So now that all cast cards are now play cards, how does that change gameplay? Let's use Heimerdinger as an example.

Heimerdinger's ability used to read like this: When you cast a spell, create a Fleeting Turret in hand with equal cost. It costs 0. Pretty nifty when you need to summon Turrets to level the Revered Inventor up!
Originally, this meant that the spell you played had to successfully activate before Heimerdinger's ability would activate.
For example: You play Death Ray - Mk 1, hoping to do some damage and get yourself a Turret to add to your arsenal.

But then, your opponent plays the dreaded Deny - preventing it from activating.

Since Deny prevented your Death Ray from being cast, Heimerdinger's ability didn't activate.
Starting with patch 3.6, here's how Heimerdinger's card appears.

Notice that Heimerdinger's ability now reads: When you PLAY a spell, create a Fleeting Turret in hand with equal cost. It costs 0.
Remember - a card is "played" once it leaves your hand into play.
Let's use the same example as above, but this time with the play mechanic.
You play Death Ray - Mk 1, hoping to do some damage and get yourself a Turret to add to your arsenal. But then, your opponent plays the dreaded Deny - preventing it from activating. While this has blocked your Death Ray, it hasn't prevented you from getting that all-important Fleeting Turret card into your hand. That's because Heimerdinger's ability now activates when you play a spell instead of it when it is cast. As soon as you played the spell, his ability went into effect, despite the spell itself being denied.
Cast being merged with Play affects more than just Heimerdinger -- any card that previously had a Cast mechanic now has a Play mechanic.
That's not the only change long-time players should be aware of, either! Take a look at how targeting has changed, as well as an update to the timing of burst and focus spells. For more information on all of the patch 3.6 changes, head on over to the patch notes.
