Sonic Mania Launches for PC, is Accidentally Online-Only

Steam users are unable to play the game in offline mode, despite Sega's insistence that the game is intended to be playable offline.
Denuvo's copy-protection system seems to be the problem.

Sonic Mania Review - A Joyous Leap Back In Time - Game Informer

Sonic Mania Release Date Possibly Revealed by Steam

SONIC MANIA UPDATE ACCIDENTALLY LEAKED!!! VIDEO, IMAGES, & NEW INFO!!!

Sonic Mania News - Nintendo Life

Sonic Origins, Sonic Wiki Zone

I dunno if you guys noticed, but Sonic CD's depot was silently updated and now it shows Linux support : r/linux_gaming

Sonic Mania Plus' Upcoming Features, Changes Accidentally Leaked By 'Sonic Mania' Patch

Sonic Chaos - Turquoise Hill Demo

Sonic Mania PC Drops Always Online Requirement Following Fan Outrage

Sonic Mania's DRM cracked, days after launch - Polygon

Sonic Mania (PC) - Mini-Revver

Beyond Good & Evil 20th Anniversary Edition Accidentally Leaked by Microsoft