Run a world of your own and watch the systems tick.
Simulation games are satisfying when systems react in believable ways and invite experimentation instead of just giving one correct path. This page collects browser games where the fun comes from operating, adjusting, observing, and learning how a model or world responds.
These picks are close relatives when you want more planning, more freedom, or a heavier layer of complexity on top.
If you want a fast way into this category, start with KUNDURUP, Vieraville, Eastshore, and DIVINE DEFENCE.
The list below adds a few more strong picks from the current simulation games selection on Rosebud Play.