Abandonware Puzzle games
Puzzle games focus purely on solving puzzles usually without much narrative. Puzzles exist in many varieties: strategic, tactical, logical, trivia, word puzzles etc.
In the Puzzle genre, you may want to play 15 x 15, 1993tris, 2010: The Graphic Action Game, 3D Lemmings Winterland, 3D Pitfall. Those are just suggestions, you are welcome to download any game!