Omega Flowey Fight Simulator -2021- is a fan-developed, browser-based interactive simulation recreating the climactic final boss battle against (often referred to as Omega Flowey) from Toby Fox’s 2015 indie role-playing game Undertale . The “-2021-” suffix indicates a specific iteration or fork of the simulator that gained traction during the COVID-19 pandemic, capitalizing on renewed interest in Undertale ’s lore and challenging gameplay.