Whether you are coding in GML for a fangame, Lua for a CYF mod, or Python for a fan remake, remember Toby Fox’s golden rule:

# After sparing Toriel global.flags["toriel_spared"] = True global.flags["toriel_killed"] = False

Since Undertale was created in GameMaker: Studio, many engines are native to the platform. is a complete GameMaker template that includes the battle and overworld systems out-of-the-box, offering an authentic feel.

If you'd like, I can write a for a character. Just let me know:

But for modders, fan-game developers, and curious programmers, the question isn't how to beat these battles, but how to script them . What makes a Sans attack pattern tick? How does Toriel’s mercy flag trigger? How can you replicate the infamous "dying soul" slow pan in GameMaker: Studio, Construct, or Unity?

Unlike real-time action games, Undertale fights are turn-based but with a twist:

toriel_attack() let pattern = []; if (player.hp <= 3 && !toriel.has_warned) toriel.say("I apologize, my child."); toriel.aim_offset = 20; // pixels away from soul toriel.has_warned = true;