Puzzles & dice
Three games with nobody to play against. Two are pure logic and the third is pure nerve, and the contrast between them is the point.
Sudoku contains no luck and no hidden information whatsoever. Every puzzle on this site can be solved by deduction alone — if you find yourself guessing, there is a inference you have missed rather than a gamble you need to take. That property is what separates a good Sudoku from a bad one, and it is why the puzzle has survived the enormous boom it went through in the mid-2000s after Wayne Gould’s puzzles began appearing in British newspapers.
Minesweeper looks similar and is fundamentally different. Most of the board yields to logic, but a well-known feature of the game is that some positions genuinely cannot be resolved by deduction and require a coin-flip. Learning Minesweeper properly means learning to identify those positions, clear everything else first, and take the guess only when there is nothing left to deduce. It reached an entire generation by being bundled with Microsoft Windows from 1990 onwards.
Farkle is the opposite of both. It is a dice game with no board and no information to gather — the only decision you ever make is whether to bank the points you have or roll again and risk losing them all. That single repeated question turns out to be enough for a genuinely good game, because the correct answer changes with how many dice are left, how far ahead you are, and how much you have already put at stake.