Gozen Match — Ruling

Effetto 0

You cannot activate this card during the Damage Step.
While a player has a face-up monster in their Monster Zone, they cannot Normal Summon, or Special Summon face-up, a monster with a different Attribute from that monster.
This card can be activated at any time, except during the Damage Step.
When this card's activation resolves, or if a monster with a different Attribute is flipped face-up while there is already a face-up monster in its controller's Monster Zone, this card's effect will apply, and that player must send monsters to the Graveyard so they only control a single Attribute. (This does not start a Chain. It also applies during the Damage Step.)
This card's effect does not involve declaring Attributes. While this card's effect is applying, it is simply impossible for a player to control face-up monsters of two different Attributes.

About this card's ① st effect:
This effect is not an activated effect. It is applied by this face-up card in the Spell & Trap Zone.