Isometric Pathfinding

Overview

Pathfinding runs on grid coordinates, not screen pixels. This skill implements A* over the walkable layer with proper diagonal handling so units take natural paths and never cut through blocked corners.

When to Use

• Units or NPCs need to move to a target around obstacles.
• Characters walk through walls or take ugly paths.
• You have a walkable layer and need movement on it.

Process

1. Run A* on grid coords using the tilemap walkable layer.
2. Define neighbors: 4-way or 8-way; for 8-way, forbid cutting blocked corners.
3. Use an admissible heuristic (octile distance for 8-way).
4. Return a path of grid tiles, then convert to screen with isometric-grid-math.
5. Smooth the path (string-pulling) to avoid zig-zag.
6. Recompute or repath when the map or target changes.
7. Cap search cost (node budget) for large maps.

heuristic (octile): dx=|x1-x2|, dy=|y1-y2|; h = (dx+dy) + (1.414-2)*min(dx,dy)

Rationalizations (Stop Lying to Yourself)

Excuse	Reality
"Straight-line movement is fine"	Units will walk into walls. Use A* on the walkable layer.
"Corner cutting looks fine"	Units clip through diagonal walls. Forbid blocked-corner cuts.

Red Flags - STOP if you catch yourself:

• Pathfinding on screen coords instead of grid coords.
• Allowing diagonal moves through blocked corners.
• No node budget so large maps freeze.

Verification

You are NOT done until every box is checked:

• A* finds paths around obstacles on the walkable layer.
• Diagonal moves never cut blocked corners.
• Path converts correctly back to screen positions.