Don't Panic - Game AI and Behavior Systems

Game AI is the bit that decides what a non-player character does next, then asks the rest of the engine to make the feet and the bullets cooperate. It is usually handwritten structure, not a model that trained overnight and developed opinions.

Before fancy graphs, people jammed modes into booleans. Chase and Flee both true is a vibe, not a design. A finite state machine fixes that: one active mode, named transitions, no illegal committees. Hierarchical machines share parent handlers; concurrent machines keep movement and combat from multiplying into one giant chart.

When tactics need "try this, else that, else the other thing," reach for a behavior tree. A sequence is a to-do list that quits at the first failure. A selector is a priority list that stops at the first success. Decorators nitpick a single child. Leaf tasks do the boring verbs: move, shoot, wait. The blackboard is the shared notepad sensors write on and tasks read from. If the notepad still says the player is in the kitchen, do not be surprised when the agent clears the kitchen with enthusiasm.

Utility scores soft preferences when many options are partly good. GOAP searches for a plan when the action vocabulary gets combinatorial. Unreal's EQS answers "where should I stand?" so the tree is not full of magic coordinates.

Decision says go there. Navigation meshes say how: walkable polygons, a path corridor, then steering so the agent arrives without forming a polite queue inside a doorway. Unity, Godot, and Recast/Detour all rhyme here. Off-mesh links are the honest admission that jumps and ladders are not ordinary polygons.

The useful panic rule: name the layer. Thrashing leaf while the world is still? Priorities. Stable leaf, no motion? Hole in the mesh. Fine path, weird gait? Locomotion. Far-away crowds melting the frame? Tick less, share sensors, shallow the tree.

Read the intro for the architecture, the cheatsheet when you forget whether a selector fails loud or quiet, Field Notes when you want the bruises, Practice for the debug rituals, and Reference when you are ready for engine docs that mean it.