I'm a hobbyist game designer, and I love looking at games for ideas on how to improve or change them for fun.
Blackjack is a simple card game played with a standard deck of playing cards. On your turn, you may draw a card from a draw deck and put it into your hand. Should you decide to abstain from drawing, you're out of the game until every player abstains. At the end of the game, the player with a hand closest to 21, without exceeding 21, wins.
I like Blackjack because its rules are simple and the game is flexible. It's easy to adapt Blackjack for multiple players or a single player. inherently, I think it's meant to be a game between a dealer and any number of players. But you can also play it as a single-player game by playing as both dealer and player. This works because while the lose condition is absolute (your hand exceeds 21), the win condition depends on the state of your opponent's hand compared to your own.
I feel like the ideal solo version of a game, in terms of game design cleverness at least, doesn't require you to play two roles. Not all game design has to be ideal or clever, and I do play and enjoy several games as two or more roles. But I like to strive for the ideal, and one game I've "solved" for solo play is Blackjack.
The key additional mechanic is "chicken", which is a generic game term implying a test of your risk tolerance. In a game of chicken, one or more people engages in something risky. The loser is the player who surrenders to safety first. You've probably seen extreme examples of it in movies like Rebel without a cause, when two stupid teenagers race beatup cars toward a cliff edge, with the winner being the one who ejects nearest the cliff edge. Do not try that at home.
Blackjack poses less of a risk than that, luckily, but can still make use of the chicken mechanic.
I've got a simple hack for a single-player "chicken" version of Blackjack:
Blackjack is a simple game, and this version makes it a true solo game. Have fun.
Header photo by Amanda Jones on Unsplash.