Can you react to opponent playing a card at beginning of their turn?

Question

Accepted Answer

No, you cannot react to your opponent simply starting their turn or playing a card at the beginning of their turn, unless that card play itself creates a reaction window.

Here is the breakdown of why based on the game rules:

### 1. No Priority during Phase Changes
You do not receive priority simply because a phase or step begins (e.g., the Start of Turn phase). As confirmed by **RiftJudge FAQ #9538** and **RiftJudge FAQ #2886**, players only receive priority to play cards or activate abilities when the opponent performs an action that creates a chain, or during a showdown.

### 2. Can you react to them "playing a card"?
It depends on the **type** of card they play:

*   **Permanents (Units or Gear):** When a player plays a permanent from their hand, it resolves immediately. According to **RiftJudge FAQ #5909** and **RiftJudge FAQ #2711**, playing a permanent does not pass priority on the chain, so there is no window for your opponent to react.
*   **Spells:** When a player plays a spell, it goes on the chain. This creates a **Closed State**, which grants the opponent an immediate window to play a [Reaction].
*   **Triggered Abilities:** If the card the opponent plays has a "When you play me" (WYPM) triggered ability, that ability is placed on the chain *after* the card enters play. This creates a window for you to play [Reaction] cards to interact with that ability (see **RiftJudge FAQ #8067**).

### Summary
*   **Phase start:** No reaction window.
*   **Playing a Unit/Gear:** No reaction window (unless it has an on-play triggered ability).
*   **Playing a Spell:** Yes, you can react because it creates a chain.

In short, you cannot react to the act of a card being played unless the rules specifically dictate that the action creates a chain (like a spell) or triggers an ability.