Bad Time Simulator

Have you heard the line “you’re gonna have a bad time”? That’s the greeting from Sans, the famous final boss of Undertale. Bad Time Simulator puts the entire Sans Fight right in your browser: press Play and you’re in the battle, with no installation and no sign-up.

What Is the Sans Fight, and Why Does It Torture Players?

The Sans Fight is the final battle of the Genocide route in Undertale. Sans has only 1 HP, yet he dodges every attack you make, then answers with bones, Gaster Blasters and gravity shifts. The developer jcw87 rebuilt this fight in Construct 2, keeping the original music and dialogue. Thanks to that, you can practice each attack on its own without replaying the whole game.

You control a red heart inside a small box. This game doesn’t ask for shooting skills, only for moving to the right spot at the right time. Every attack has a safe answer, and every death teaches you something new.

Start Playing in One Minute

1. Press Play on the page and use a keyboard.
2. Choose a mode: Normal, Practice, Single attack, Custom attack or Endless.
3. On your turn, choose FIGHT and press Z when the bar is in the center. Sans will dodge, so keep attacking.
4. On Sans’s turn, move the heart to avoid anything white. When you see light-blue bones, stand completely still.

Controls

It’s best to turn on fullscreen using the icon under the game frame, since the battle box is quite small.

Tips for Beating the Sans Fight, From Someone Who Has Died Many Times

Practice Each Attack First

Don’t try to restart from the beginning forty times. Go into Single attack, repeat the attack that kills you until it gets boring, then return to Normal.

Tap, Don’t Hold

The heart moves very fast, so most deaths come from overshooting a gap. A few short taps will put you exactly where you want to stand.

Light-Blue Bones Mean Stand Still

The reflex to dodge is exactly what kills you. Take your hands off the keys and let the bones pass through.

Listen to the Music to Predict Attacks

Megalovania acts as the clock for the whole fight. Attacks change with each phrase of the music, so after a few runs you’ll be able to guess what comes next.

Watch Out for Karmic Retribution (KR)

The purple part of your health keeps draining. A few small hits early on can be more dangerous than one big hit, so a clean start matters more than healing. Use items once the drain has stopped.

The Special Attack Just Takes Patience

Sans stands there waiting for you. Wait it out, then survive the final bone gauntlet when you try to end your turn.

Frequently Asked Questions About Bad Time Simulator

The Sans Fight looks chaotic, but it is actually a sequence of attacks that follow clear patterns. Beating it is one of the most satisfying feelings in browser games. Open Bad Time Simulator, pick Practice, and give it a try today.