Surprise, surprise! The ESRB has given Sonic Mania an E rating for mild cartoon violence. This isn't really unexpected, but if anyone would like to read more about their decision, you can find the rating summary below:
This is an action-platformer in which players assume the role of Sonic as he zooms around colorful “zones” and attempts to defeat Dr. Eggman. As players run and jump through whimsical environments, they can jump on enemies' heads, causing them to transform into small woodland creatures. Boss battles sometimes depict characters shooting "cartoony" bombs and/or oversized missles; Sonic reacts to damage by losing coin-like rings and falling off the screen when defeated.