There are two game states during the Duel, "open" and "closed".
Whenever a player performs an action, the game state is "closed". If nothing is going on, and neither player wishes to do anything, the game state is "open". Technically, this means:
- IF the Turn Player has the chance to activate the next fast effect...
- AND the turn player passes to the opponent...
- AND the opponent then passes back...
- AND no Chain is currently being formed...
…then the game state is "open".
If the game state is "open", the turn player may perform any of the appropriate actions, those actions are:
- Normal draw (during the Draw Phase)
- Normal Summon
- Normal Set
- Perform a Special Summon that does not start a Chain (including Xyz Summon, Synchro Summon)
- Change a monster's Battle Position
- Attempt to move to the next Phase/Step
- Declare an attack (during the Battle Phase)
- Activate an Ignition or Ignition-like Effect
- Activate a Spell Speed 1 Spell Card
- Activate a fast effect
If the game state is "closed", then only fast effects can be activated, dependent on Fast Effect Timing rules.