After over 150 hours of play, I have finally completed 100% clear in Chaos Seed!
This game is well worth the time. It is enjoyable all the way. Some games may last 100 hours, but none has as intensive game play as Chaos Seed all the way.
Initially, I was too absorbed in Cave Construction that I almost overlooked the rather unique "parallel worlds" world view, and the intriguing scenarios and events. As I saw more scenario endings, I began to realize the brilliant "cause and effect" relationship between the parallel worlds. The events are not bound by time relationship, so the story is, in my opinion, one notch above those with time travel themes, such as that in Chrono Trigger.
Cave Construction is always interesting, because when making a room, the player is trying to optimize among many factors: location, size (and cost), resources, fung-shui element, and room type. Do I build a huge room, despite the high cost, and make this room the 'main' room (with lots of resources and lots of improvements) in my Cave? Do I just build a room for the fung-shui and forget about the rest, or do I forget the fung-shui and concentrate on the rest, or do I wait and try to get a better balance in a later turn? Lots of Sentan resources but yet more Energy resources here; do I build a Production room, or do I build a Sentan room because it seems more needed here? Do I build a room, or do I simply build a crossroads? And so on. And, movement around my own Cave is interesting too. In Chaos Seed, one can build a good Cave, or one can build a better Cave; and there are many ways to build a better Cave. Although a game where you 'just build something' may be enjoyable, a game where you're building something for a specific purpose would be that much more enjoyable.
Again, I heartily recommend Chaos Seed to all hard-core gamers. And, if you think the SFC is obsolete, why not try the coming Sega Saturn version?