reddit

“
For nice pictures, see
David Molnar's
page and Helen Joyce's
page.
An applet.
Existence of a winning strategy
If P has a largest element 1, different from 0, then a trivial
strategy-stealing argument shows that the first player wins.
(If picking 1 does not win, it is because the opponent has
the devastating reply a. But in that case the first player wins
by starting with a.)
” source...