Trigon (Japan)

In Lightning Fighters and Trigon, the original Japanese version, there are different rules depending on whether you start the game with one or two players. In a one-player game, you start with no bombs, and when you die the game restarts you at a checkpoint. In a two-player game, each life starts with one bomb, and when you die you respawn in place. There are some powerups that only appear in a two-player game and one that only appears in a one-player game. The game type cannot be changed once the game starts. A second player cannot join an originally one-player game; conversely, if one player dies in a two-player game the game remains in two-player mode and the second player can rejoin at any time.

In Lightning Fighters, even if you start a one-player game, the game is always in two-player mode: you respawn in place when you die and you start each life with one bomb stocked. This means that a second player can join midway into a one-player game. Unfortunately it also means that the powerup that only appears in one-player games in the other versions, does not appear at all in the US version.