Bad Time Simulator

Rating:⭐ 4.2 (1,221 votes)

Technology:HTML5

Platforms:Browser

About Bad Time Simulator

Bad Time Simulator is a fan-made browser recreation of the Sans boss encounter from Undertale. Created by Jcw87, it isolates the challenging battle and makes it possible to replay or practice it without progressing through the original game.

You control a small heart inside a battle box while Sans launches sequences of bones, beams, platforms, and gravity-based attacks. The patterns become increasingly complicated, requiring accurate movement, memorization, and patience.

This is not a conventional action game where attacking repeatedly guarantees victory. Sans avoids each attempted hit until he eventually becomes too tired to continue. Your real objective is to survive every enemy turn and continue selecting FIGHT when the menu returns.

Bad Time Simulator runs directly in a desktop browser and uses a compact keyboard control scheme. It is an unofficial fan project and is not developed or published by Undertale creator Toby Fox.

How to Play Bad Time Simulator

Select a mode and begin the encounter. During your turn, navigate the battle menu and confirm an action. During Sans’ turn, concentrate entirely on keeping the heart away from incoming hazards.

The basic battle cycle works as follows:

Select FIGHT from the action menu.
Press the confirm key when the timing bar approaches the center.
Prepare for the heart to enter the battle box.
Dodge bones, beams, and other attack patterns.
Adjust when the heart changes from red to blue.
Use an ITEM to recover health when necessary.
Continue attacking when your turn returns.
Survive every phase until Sans can no longer evade.

The attacks follow recognizable sequences. Do not depend entirely on reaction speed; learn where each pattern begins and move toward a safe position before the screen becomes crowded.

Controls

Use the following keyboard controls:

Action

Control

Move the heart

Arrow Keys or W, A, S, D

Jump while the soul is blue

Up Arrow or W

Confirm selections and attack

Z or Enter

Cancel, return, or skip dialogue

X or Shift

Open supported menu functions

C or Ctrl

Click the game window once if the keyboard is controlling the browser page instead of the character.

Short directional taps provide greater precision than holding a key continuously. Diagonal movement is useful during open bullet patterns, while single-direction movement is more reliable in narrow gaps.

Soul Modes, Attacks, and Game Modes

Understanding the rules behind each hazard is more important than trying to move constantly.

Element

Behavior

Correct Response

Red soul

Moves freely in four directions

Dodge with small, controlled inputs

Blue soul

Is affected by gravity

Jump and land on safe platforms

White bones

Cause damage on contact

Move around or jump over them

Light-blue bones

Hurt the soul while it is moving

Remain completely still

Gaster Blasters

Fire beams across the battle box

Move away before the beam activates

KR damage

Continues draining health after a hit

Avoid repeated contact and recover carefully

Normal Mode

Presents the complete battle

Use after learning the major patterns

Practice Mode

Supports training and repeated attempts

Learn difficult sections safely

Single Attack

Repeats a selected pattern

Build precise muscle memory

Endless Mode

Continues generating attacks

Test consistency and endurance

Custom Attack

Uses a chosen sequence in supported builds

Create or load specialized challenges

Blue attacks reverse the usual instinct to dodge. If a light-blue bone approaches, release every movement key and allow it to pass through the stationary soul.

Beginner Tips for Bad Time Simulator

Begin with Practice Mode. Learning individual patterns is more productive than repeatedly failing at the same point in a full battle.

Use small taps. Holding a direction often carries the heart too far and into another hazard.

Watch the soul’s color. Red and blue movement follow different rules, so adjust immediately when the change occurs.

Remain still during light-blue bones. Even a tiny movement input can cause damage.

Focus on survival rather than the attack meter. Sans will dodge regardless of timing during most of the encounter.

Use healing items strategically. Recover when health is low enough to justify giving Sans another attack turn.

Take short breaks after repeated failures. Precise movement becomes much harder when frustration causes rushed inputs.

Advanced Bad Time Simulator Strategy

Memorize the opening movement of every pattern. The first second often determines whether the rest of the sequence will be controlled or chaotic.

Move toward safe zones before attacks fully develop. Waiting until bones fill the box leaves fewer escape routes.

Use minimal jumps in blue-soul sections. Holding the jump key too long may send the heart into overhead hazards. Release early when a short jump is sufficient.

Separate patterns into segments. Learn the opening, middle, and ending movements independently before attempting one continuous sequence.

Preserve health during familiar attacks. Every avoidable hit reduces the margin for error in later phases, where the patterns become faster and longer.

Practice the final gauntlet separately when the mode allows it. Reaching that phase repeatedly through Normal Mode is an inefficient way to learn its timing.

Maintain a relaxed grip on the movement keys. Panic inputs cause overcorrection, especially when the heart is pushed or gravity changes direction.