In the startup industry you'll find lots of greenfield projects, but very few where working only 4 hours a day is acceptable. Startups tend to need to get a lot of work done, relatively quickly, with a very small team. This is just the most effective way to build a business during the startup phase.
However, you will also find lots of startups have very flexible work hours as long as you get a reasonable amount of work done every week. Additionally, depending on your skill level and role within the startup it is likely that you'll be working on lots of different types of projects from day to day, which for me personally has always been enough to keep me enjoying what I do for a living, even though I'm usually working 40+ hours per week.
And some startups are very open to you contributing code back to the open source community. (Especially Node.js startups, where publishing NPM modules is just part of being a member of the ecosystem.) For me personally this also gives me that feeling of pleasure that ordinary work related coding might not always.
However, you will also find lots of startups have very flexible work hours as long as you get a reasonable amount of work done every week. Additionally, depending on your skill level and role within the startup it is likely that you'll be working on lots of different types of projects from day to day, which for me personally has always been enough to keep me enjoying what I do for a living, even though I'm usually working 40+ hours per week.
And some startups are very open to you contributing code back to the open source community. (Especially Node.js startups, where publishing NPM modules is just part of being a member of the ecosystem.) For me personally this also gives me that feeling of pleasure that ordinary work related coding might not always.