If you own the original Undertale but don't have a save file ready, use Flowey’s Time Machine . It’s a powerful web tool that lets you generate a custom save file at any point in the game—including right before the Omega Flowey encounter.
For those who want to take the fight on the go, there are dedicated Android apps that recreate the experience for touchscreens. omega flowey fight simulator free
Whether you are playing the full game or the simulator, Omega Flowey is a beast. Here is how to survive his multi-stage assault: If you own the original Undertale but don't