// In Papyrus attack step event if (soul_color == "blue") vspeed += gravity; if (place_meeting(x, y+1, ground)) vspeed = -jump_strength;

| Tool | Language | Best for | Undertale-style feature | |------|-----------|----------|--------------------------| | | GML | Most faithful recreation | Built-in collision & bullet systems | | Unity | C# | Cross-platform, advanced effects | Custom Shaders for bullet patterns | | Godot | GDScript | Open-source, light | AnimationTree for SOUL movement | | Construct 3 | Visual scripting | No-code rapid prototyping | Event sheets for turn logic | | FNF: Psych Engine | Haxe | Rhythm-based battles | Already has note-based attack patterns |

if global.kill_count >= 20 and global.area == "Last Corridor": sans.prepare_battle() sans.dialogue = "you've been busy, huh?" global.genocide_sans_trigger = True You don’t need to reverse-engineer Undertale’s original code. Here are the best modern tools:

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?