Sans is unique in that he’s the most popular character in Undertale while also providing one of the most frustrating boss fights the game has to offer.
If you’d like to relive the experience of wrapping up a Genocide run without playing through the whole game again, this “Bad Time Simulator” lets you face the cool skeleton dude right in your browser. It’s a couple years old, sure, but it’s still neat. It even works on mobile browsers!
What’s cool is that it’s not just the fight. You can play through it like normal, sure, but there’s also a practice mode, an endless mode, and it even gives you the ability to repeatedly test your mettle against a single attack. I can see this being a huge help for anyone trying to nail down Sans’ patterns.
I didn’t get very far but I’m sure there are better Undertale players than me out there. Check it out.