When Nintendo’s beloved CEO Satoru Iwata passed away last year, he left a lasting legacy for his numerous contributions to the gaming industry. But while Iwata was instrumental to many of Nintendo’s other successes, his role in the development of the popular augmented reality app Pokémon Go, can be considered one of the most memorable, for the effort that he put into the game during his final days.

During his last few years, Iwata laid the groundwork to what would later become Pokémon Go. Conceived in 2014, Iwata and his close friend Tsunekazu Ishihara of The Pokémon Company worked together to develop an April Fools’ Day game called Pokémon Challenge, in collaboration with Google.

Ishihara, who was a fan of Niantic Inc’s earlier augmented reality game Ingress, thought that a similar game mechanic can be utilized for Pokémon Go.

Already enduring an ailment, Iwata was determined to further develop the concept into something much more. After his surgery in June 2014, Iwata was even quoted as saying, “I still have unfinished business.”

Iwata would later adopt the idea the following year, when Nintendo made a decision in March 2015 to enter mobile gaming. Iwata wanted to create a game that was traditionally Nintendo under his own direction, according to Nikkei. The work on Pokémon Go began that year.

In his hospital room, up until his last moment, Iwata reportedly continued to work on Pokémon Go. Using his favorite PC, he discussed details of the game with Ishihara. He passed away, a few months later.

When the game was announced in September 2015, two months after Iwata’s death, Ishihara dedicated his speech to his friend.

Pokémon Go has been enjoying tremendous success since its launch last month. And while the Niantic Inc team has been getting their well-deserved praise (and share of criticisms) for the massive global hit, Iwata should also be remembered for his magnificent swan song and gift to the Pokémon fans and the gaming world in general.