A suggestion: work on one project until it's finished. Each completed project opens certain features of the game, and you can be enjoying those features of the first completed project while you work on the next one. I'm not going to spoil the fun of discovery by telling you what the features associated with each project are. In some cases I don't know or am not sure. The one thing I'm pretty sure about is that I don't know everything that the projects do for you. I'm pretty sure the bridge lets you get into the Northern Lands, for instance (can't fool me!) but if it does other things I don't know.