Now that E3 2021 is officially over, it’s safe to say thatMetroid Dreadwas the biggest shock of the show. Nintendo filled fans’ wildest dreams with the first original Metroid game in 19 years, which is a proper sequel to theGame Boy AdvancetitleMetroid Fusion.

What some fans might not realize, though, is thatMetroid Dreadisn’t a brand-new title for Nintendo; it’s been in the works for 15 years.

During Nintendo’s Treehouse Live event following its Direct presentation, fans got a much deeper dive into the game with a gameplay demo and insight into its development history.Metroid Dreadproducer Yoshio Sakamoto explained that the original concept for the game was initially too ahead of its time to become a reality.

“Actually, the idea forMetroid Dreadfirst came up about 15 years ago,” says Sakamoto during the video. “However, we gave up on the idea at the time, because we felt the technology back then just couldn’t properly bring the concept to life. We did have a chance to try again after that, but we felt like we still couldn’t create the game as originally imagined, so we ceased development at that point.”

That timeline tracks when looking back through news from the past decade. In 2005, IGN reported thatMetroid Dreadwas featured on aninternal list of software planned for the Nintendo DS. The game reportedly was shownbehind the scenes at E3 2009as a working prototype. However, that was really the last time anyone saw it.

The only other time we saw a reference toMetroid Dreadwas inMetroid Prime 3: Corruption. A scannable piece of lore in the game reads, “Experiment status report update: Metroid project “Dread” is nearing the final stages of completion.” At the time, players were certain that it was a cheeky confirmation that the game was coming, but Retro Studios denied any connection. It even went as far as to change the text in the Japanese version to “The development of Dread-Class Turret is going well.”

According to Sakamoto, the project was only revived due to MercurySteam’s work onMetroid: Samus Returns, the Nintendo 3DS remake ofMetroid 2. Sakamoto was impressed with the team’s work on the title and felt that their style was finally the right fit forDread‘s ambitions.

“Technically, they’re very skilled. They also have great taste,” says Sakamoto. “But more than anything, they have an incredible understanding of Metroid games. I was confident that partnering with this wonderful team would finally allow us to bringMetroid Dreadto life.”

Metroid Dreadis coming to Nintendo Switch on October 8.