diff --git a/accessor.go b/accessor.go
new file mode 100644
index 0000000..a28e8ef
--- /dev/null
+++ b/accessor.go
@@ -0,0 +1,9 @@
+package types
+
+import "image/color"
+
+// returns the node at the given position, nil if no node found
+type NodeAccessor func(pos *Pos) (*Node, error)
+
+// resolves the node-name and param2 to a color, nil if no color-mapping found
+type ColorResolver func(name string, param2 int) *color.RGBA