My first foray into game design was through Media Molecule's LittleBigPlanet series.
In 2011 I made Sonic Adventure 3, a (since lost) series of levels based on Sega's Sonic the Hedgehog. They were well received in the community, getting thousands plays and even a mention on G4TV.
The "Sackbot" I created for this series went on to be used by other creators in new and innovative ways.
A few years later I created Sonic Elements, a spiritual successor to SA3. Though the player-base of LBP2 had decreased since my first series, they were well-received and are still available to play today on both LBP2 and 3.