Undertale Battle Menu Guide: ACT, MERCY and Surviving Your First Fight

When you meet a monster, Undertale changes from the room view to a black battle screen. The monster appears near the top. A white-bordered box in the middle shows messages and your choices. Along the bottom are four orange commands. You can take a moment to read: the fight does not move to its next step until you make a choice.

• FIGHT is the far-left command. It attacks. You do not have to choose it for every encounter.
• ACT is second from the left. It lets you interact with a monster or check its information.
• ITEM is third. It opens the items you are carrying, including any healing item you have.
• MERCY is far right. It is where you try to spare a monster instead of defeating it.

Watch HP before making your next choice. The number beside the small colored bar tells you how much health you have left. If an enemy attack reduces it, ITEM may be more useful than repeating the same ACT choice.

On PC, the red heart marks your current choice. Move it with the arrow keys and confirm with Z or Enter. The official Undertale help page also lists Shift as an alternative to X for going back, so X or Shift can help if you open the wrong menu. If you play with a controller, use the direction and confirm buttons shown by your version of the game; do not assume its labels match a PC keyboard.

1. At the row of four commands, move the red heart under the command you want. Look at the word inside the orange frame, not just the tiny icon beside it.
2. Press Z or Enter once to open that command. If another list appears, move the heart to a line in that list and confirm again.
3. If you are still choosing from a list and want a different command, use X or Shift to go back. Once you finish a choice and the monster starts an attack, you cannot undo that turn; focus on dodging instead.

1. Find ACT, the second button at the bottom, and confirm it. If more than one monster is on screen, choose which monster you mean first. The selected monster’s actions then appear in the white box.
2. Read the actions before choosing. Check is useful when you want information. Other words describe ways to interact, and they change from monster to monster. The screenshot happens to offer Hug; do not expect Hug in every fight.
3. Move the red heart beside an action and confirm. Read the new line of text carefully. It may tell you how the monster reacted or hint at what to try next. After your choice, be ready for its attack phase.

ACT is not a single “make friends” button. You may need to try a different action, repeat an action, or respond to the monster’s clue. If one choice does not end the encounter, that is normal.

If you see two or three sprites across the top, do not assume one ACT result applies to everyone. Choose a target by name when the game asks. Use the text box to notice which monster reacted; the next turn may need a different target. The bottom menu stays in the same place, so you can always return to ACT or MERCY after surviving an attack.

You do not need to memorise every monster on sight. Read the encounter message, pick one target, see how it responds, then decide what to do next. That one-at-a-time routine is much easier to follow than pressing through the menus without reading.

1. After your choice, watch the middle of the screen. A white-bordered battle box appears, often changing size or position. Find your red heart inside it.
2. Move the heart with the arrow keys, staying inside the box. Follow the white shapes as they travel toward you, and steer into a clear gap. Do not keep looking at the four orange commands while the attack is moving.
3. When the attack ends, the commands return. Look at your HP. If it dropped, decide whether to use an item before trying another ACT or MERCY choice.

Different monsters send different shapes and patterns. The safe direction can change each time, but the basic job stays the same: locate the heart first, read the approaching shapes, then move through open space. If you take a hit, check HP when your next command turn begins.

ITEM is the third orange command, between ACT and MERCY. It opens the things you currently carry. If you have a healing item and your HP is low, move the red heart to that item and confirm. Read its on-screen description before you use it; different items have different effects.

Using an item takes your turn, so be ready for another enemy attack afterward. If the list has no useful healing item, return to the main commands with X or Shift and decide whether to ACT, FIGHT or try MERCY instead. This is why it helps to glance at HP as soon as an attack ends.

Find MERCY at the far right of the bottom row. Open it and choose Spare. Some monsters can be spared immediately; others respond to what you do with ACT first. If choosing Spare does not end this battle, do not keep pressing it blindly. Read the monster’s dialogue, try an ACT choice that fits its reaction, survive the next attack, then check MERCY again.

A failed Spare attempt does not mean you must FIGHT. It means you need to understand that particular encounter. Undertale’s official description specifically says you can negotiate out of danger instead of destroying everyone. The path through a fight can be different for different monsters.

If you choose FIGHT instead, use the far-left button. The game asks you to time an attack rather than simply selecting a word. Damage and the choices you make can affect how your playthrough unfolds. If you are aiming to avoid kills, pause before selecting FIGHT and explore ACT and MERCY first.

Once the battle ends, you return to a room. Look for a small glowing yellow star along your route. Walk up to it and use the confirm button to open the save message, then follow the on-screen prompt. It is worth saving after a tough encounter before exploring the next area.

The star is not part of the four-command battle menu; it appears while you are walking around. If you do not see one immediately, keep exploring the room normally. You can still take your time with text, characters and paths between battles.

• Cannot tell what to press? Look at the four words along the bottom: FIGHT / ACT / ITEM / MERCY.
• An ACT did not finish the encounter? Read the new dialogue, try a different interaction, then check MERCY after the next attack.
• White shapes are moving? Forget the menu for a moment and move the red heart inside its white box.
• HP is getting low? Open ITEM on your next command turn if you have something useful.
• Several monsters are visible? Choose a specific target when ACT asks; their reactions are separate.
• Want to avoid a kill? Explore ACT and MERCY before choosing FIGHT.

The battle screen gives you information in a repeatable order: read the monster and message, choose one command, dodge with the red heart, then look at the new message and your HP. Once you recognise that loop, the menu becomes a conversation you can follow instead of a row of mystery buttons.