Infinitesimals occur often in no-capture go, aka gone, a variant of go in which passes, captures, and suicide are illegal, and the player without a move loses.
Star (*)
The infinitesimal, STAR (*), is like a dame in go. Each player can move to 0. The first player wins in a Star.
After each player has one move, for a zero.
Down (v)
Down (v) is a negative infinitesimal (White wins). White can move to 0, Black can move to *.
The opposite of Down is Up (^).
After each player has two moves, for 0.
After each player can move to 0.
After each player has one move, for a zero.
Star-2 (*2)
Star-2 is like a Nim heap of size two. Each player can move to * or 0.
and are miai. Now neither player can move.
Or this position could be reached, where each player has one move, also a zero.
Another reversal.
Now each player can move to 0.
After each player has one move, for a zero.
After each player has one move.
(Note that in this * the players have different moves.)
It may not be obvious that this is a zero. There are some variations in the remaining play.
After each player has one move, still a zero.
(OC, with White to play the play could go - .)
After each player has one move, still zero.
(And the play could also go - .)
After each player can move to 0.
After each player has one move, for zero.
After each player has one move.
^* = {0,* | 0}. As the name suggests, it is equivalent to the sum of ^ and *.
After each player has one move, for a zero.
After each player has one move.
After each player has one move, for a zero.
leaves a * in the top left corner.