Undyne the Undying Simulator

How to Play Undyne the Undying Simulator

Undyne the Undying Simulator lets you play a fan recreation of the Undyne boss encounter from Undertale without playing through the story first. The embedded game is titled Undyne the Undying Fight. Here you can start the battle, learn its shield and movement controls, and check the available difficulty and display options.

Click the website's Play button. If a green flag appears inside the game, click it to open the title menu. Select Play with the arrow keys and press Z. For your first attempt, leave Hard Mode off in Options.

The heart changes how you defend. With a green soul, turn your shield toward incoming arrows rather than trying to move out of their way. With a red soul, use the arrow keys to move through the box and avoid spears. Between attacks, use the battle menu to choose your action; Z confirms and X cancels where supported.

Controls: Shield, Movement, and Menus

These controls apply to the version on this page. WASD and Enter are not listed as substitutes. Click inside the game if the menu does not respond, especially after using the site's Search field.

About This Undyne Fan Battle

Undyne the Undying Fight is a fan-made battle by tripoid, based on Undertale by Toby Fox. It focuses on the encounter with Undyne in her Undying form, combining directional shield defense with free-moving spear-dodging sections.

This is a standalone battle, not the full Undertale story or a save-file editor. You do not need to complete a route before opening it. Treat its timing and difficulty options as features of this particular recreation: a successful dodge here is not a guarantee of identical behavior in the original game.

Battle Options and Difficulty

• Play: begin the battle. The default has Hard Mode off, making it the sensible starting point for learning the shield controls and attack sequence.
• Hard Mode: toggle this in Options before starting if you want to try the alternate difficulty setting. Learn the default battle first rather than changing difficulty while you are still figuring out the controls.
• Screen Shake: turn the camera-shake effect off if movement of the whole screen makes it harder to follow incoming arrows. This is a presentation setting, not a separate training mode.
• FPS: toggle the on-screen frame-rate display. It is a display option, not a slow-motion practice setting.

This menu does not offer Bad Time Simulator's Practice, Single Attack, or Endless modes. The website's Restart button reloads the game; it does not skip directly to a chosen attack.

Tips for Blocking Arrows and Dodging Spears

• Check the soul color before reacting. In green sections, pressing a direction turns the shield instead of moving the heart. If you keep trying to run away from arrows, reset your plan: defend the side they are approaching from.
• Read the next incoming arrow, not just the last one. Holding the direction that blocked the previous hit leaves another side exposed. Track the arrival order and change the shield direction for the next impact.
• Release one direction before switching to another. When a sequence changes sides rapidly, overlapping key presses can make it harder to control the shield deliberately. Practise distinct directional inputs before trying to speed up.
• Change from blocking to movement when the soul turns red. Staying still to face a spear is no longer a defense. Move into a visible gap and leave space to adjust instead of immediately backing into a corner.
• Make small corrections in tight spear patterns. A long sweep across the box can cross several projectiles. Follow the nearest open space first, then adjust as the pattern develops.
• Use Options to remove visual distractions. If screen movement makes arrow direction difficult to read, switch Screen Shake off and keep Hard Mode off while learning. Change one setting at a time so you can tell what helped.