Star Citizen was first unveiled to the world back on October 10, 2012, with a promise to revive the space sim genre on an unprecedented scale. Cloud Imperium, the studio behind the game, initially chose to crowdfund it through Kickstarter but switched to its own platform later once the project expanded in scope. Nearly 14 years later, Star Citizen has just crossed $1 billion in total funding, and there's still no release date in sight.
To be clear, you can play Star Citizen right now; the game does exist in an alpha state with most of the promised features already included, but it's riddled with bugs. Cloud Imperium releases timely updates to add new items and gameplay, along with some very expensive microtransactions. If you back the project, you're given a pledge ship that should be playable in-game... in most cases.