Sonic & All-Stars Racing Transformed's iOS and Android versions have made the transition to free-to-play.
The esteemed racing game launched earlier this year on mobile devices for £2.99 / $4.99 and added Shenmue's leading man Ryo Hazuki, along with a new World Tour mode and both daily and weekly challenges.
Those who purchased the game prior to it going free-to-play will retain a VIP pass that unlocks Sonic and three other characters, as well as keeps the game ad-free.
Micro-transactions help speed up progression and allow you to unlock added tracks, characters and difficulty settings.
A new update for the game will be out on 29th April that will add Wreck-It Ralph and Metal Sonic to its roster of racers. Additionally, there will be new OutRun Bay and Sonic Colours' Galactic Parade courses along with a new World Tour Chapter and Boss Cup Grand Prix.
Eurogamer's racing expert Martin Robinson really enjoyed Sonic & All-Stars Racing Transformed when it launched on Wii U, PS3 and Xbox 360 in 2012. "This manages to be more than just a tribute to the great and good of Sega's past - it does enough to earn its own place alongside them," he wrote in his review of the PS3 version of Sonic & All-Stars Racing Transformed.