probaby first released onto DOS in 1991, Sherlock by Everett Kaser is this fascinatingly weird little puzzle game that seems to almost but not quite prefigure sudoku. it is cute and fun and good and will only cost you six dollars to buy Sherlock Zen, the android version which is still legit good (and doesn't have any mictotransactions or ads because the Spirit of Shareware live on even in these dark times.)
the goal is simple: each icon has a place it has to go! your job is to use the clues around the outside of the grid to whittle away possibilities until only the correct solution remains. hence the name. vertical clues at the bottom tell you about columns, so in the picture above we know that the orange is in the same column as the railroad sign! and the horizontal clues on the side tell you about rows. we know that the green guy, already placed in the grid by the game, has the letter e in a column next to him. but remember that the clue doesn't show direction! the e may be on his right or his left side! but it isn't anywhere else, including directly below him.
this game has a lot of rules, and they're hard to rememer all of them your first few times playing! the instructions even explicitly encourage you to press the hint button as a method of learning. but i don't think the game is obtuse, no information is hidden or anything. you just have to learn a bit and you'll be fine!
if you want a basically free experience, the always wonderful internet archive has a copy of the original shareware game. it only asks you to pay if you've played for a few days, and it will probably be ok to buy the android version! i haven't actually checked with everett. there's also the windows version and some of his other games!
and while we're here, let's use cohost's new editor to show a playthrough of the puzzle above! if you'd like to join me, you can play the exact same puzzle in zen sherlock, puzzle 1235.