Ascending in Complexity

Pixels Filling Squares  https://www.kongregate.com/games/Moczan/pixels-filling-squares-3-0
Idlefall                https://www.kongregate.com/games/truefire/idlefall
Zombidle                https://www.kongregate.com/games/BerzerkStudio/zombidle
Press the Button        https://www.kongregate.com/games/truefire/press-the-button
The Perfect Tower       https://www.kongregate.com/games/XmmmX99/the-perfect-tower
Tabletop Idle           https://www.kongregate.com/games/omgnoob191/tabletop-idle
Clickpocalypse 2        https://minmaxia.com/c2/
Idle Wizard             https://www.kongregate.com/games/TwoWizards/idle-wizard
Idle Raiders: 2nd run   https://irsr.games.pitforest.de/
Realm Grinder           https://www.kongregate.com/games/DivineGames/realm-grinder (also free on steam)
Idle Sword 2            https://www.kongregate.com/games/laFunk/idle-sword-2
Idle Loops              http://stopsign.github.io/idleLoops/
Idle Accelerator        https://www.kongregate.com/games/Arkshija/idle-accelerator
Idling to Rule the Gods https://www.kongregate.com/games/Ryu82/idling-to-become-god
NGU Idle                https://www.kongregate.com/games/somethingggg/ngu-idle