Reus is a simple game.
What it lacks in depth it makes up for with gameplay that keeps you involved with what’s happening in the various areas of your world. Balance out the demands in all of your established biomes and the people will be happy. Fail to do so and you’ll see wholesale revolt by your populations.
It is quick and easy to get into this game: learn the four biomes and what role the associated giant performs and you’re good to go. The game helps you out by giving you progressively more difficult challenges to meet before advancing to the next level.
Is it re-playable? Most definitely, and I would make it part of the gameplay. By this I mean that you have a countdown timer in the “Era” mode which is like a ‘campaign’ mode (I use the term loosely) where you have to successfully complete all the challenges before unlocking the next level (longer countdown, different challenges). Endless re-playability, but some might say endless repetitiveness.
Unfortunately that’s all there is to Reus and while there is no defined end game (besides dying), you can certainly achieve everything there is to achieve in the “Freeplay” mode (no countdown timer). While I do recommend playing this game (positive Steam rating), I cannot call it a good game; it is mediocre at best because of how limited the gameplay is.