added square euclidean at the dismay of many theoretical mathematicians (it's inadmissible) (but it's really fast)

astar.go

@@ -109,6 +109,10 @@ func (a *AStar) SetHeuristic(heuristic int32) {
 		a.heuristic = func(x int, y int, endX int, endY int) float32 {
 			return float32(math.Max(float64(x-endX), float64(y-endY))) // Chebyshev distance
 		}
+	case 3:
+		a.heuristic = func(x int, y int, endX int, endY int) float32 {
+			return float32(math.Pow(float64(x-endX), 2) + math.Pow(float64(y-endY), 2)) // Squared Euclidean (extremely fast but not optimal/inadmissible)
+		}
 	}
 }
 

main.go

@@ -299,7 +299,7 @@ func main() {
 	toolDropdownOpen := false
 	var tex texSync // GPU uploads: partial rects while painting; full after path resets
 
-	heuristicOptions := []string{"Manhattan", "Euclidean", "Chebyshev"}
+	heuristicOptions := []string{"Manhattan", "Euclidean", "Chebyshev", "Squared Euclidean"}
 	heuristicOptionsText := strings.Join(heuristicOptions, ";")
 	activeHeuristic := int32(0)
 	heuristicDropdownOpen := false