This is the sentinel page for the game.
You should always have a sentinel page for an interactive game because the controls are non-standard, and screen reader users will need the given context in order to be properly on-boarded.
There is documentation available.
If you are using a screen reader, clicking the "Play Game" button will launch the game itself and give it focus. Once it has focus, you can play the rest of the game using simple arrow keys, the space bar, and a few common keyboard commands. If you leave the game's focus, you may need to reload the page to continue playing.
At any time in the game, you may press "H" for help, or you may press "S" to summarize the current state of the game and the choice that is in front of you.
For instance, if you are being offered a choice, pressing "H" will tell you to use the arrow keys to select items and space bar to confirm your choice. Pressing "S" will re-speak the choice you are being offered.