Atomar

Atomar Chess is a variant invented by Nick Long. From the official rules file (PDF):

Atomar is a slight modification of Modern Atomic Chess. There are a few subtle differences that transform Atomic Chess into a new and different game. Many new players don’t enjoy or understand a few quirks of the variant when they begin learning & playing Atomic Chess. Atomar attempts to address these issues, while balancing the variant more. The balance is accomplished by the following rule additions:

• No checks or checkmates exist. You must capture the King to win.
• The Kings have developed Royal Immunity and Diplomacy.
• A King is immune to all explosions (Immunity).
• Kings can capture pieces, and when they do so, it causes an explosion just like any other capture. They cannot capture the opposing king (Diplomacy). They can move next to each other, but cannot capture the other king.

The other rules of Atomic Chess remain the same for Atomar Chess, but a KvK endgame is
always an enforced draw because the Kings cannot capture one another.