diff --git a/src/planner.cpp b/src/planner.cpp
index 6029b53..0940b95 100644
--- a/src/planner.cpp
+++ b/src/planner.cpp
@@ -31,6 +31,25 @@ Dictionary Goal::get_goal_state() const {
 
 #undef CLASSNAME // !Goal
 
+PlannerNode PlannerNode::goal_node(WorldState const &goal)  {
+    return PlannerNode{
+        goal, {}, {}
+    };
+}
+
+PlannerNode PlannerNode::new_node_along(Ref<Action> action) const {
+    PlannerNode new_node{
+        action->prerequisites,
+        action->effects,
+        action,
+    };
+    for(WorldProperty const &prop : this->state)
+        new_node.state.insert(prop.key, prop.value);
+    for(WorldProperty const &prop : this->open_requirements)
+        new_node.open_requirements.insert(prop.key, prop.value);
+    return new_node;
+}
+
 void Planner::_bind_methods() {
 #define CLASSNAME Planner
     GDPROPERTY_HINTED(actions, Variant::ARRAY, PROPERTY_HINT_ARRAY_TYPE, GDRESOURCETYPE(Action));
diff --git a/src/planner.hpp b/src/planner.hpp
index 6e84864..6fa4824 100644
--- a/src/planner.hpp
+++ b/src/planner.hpp
@@ -49,24 +49,9 @@ struct PlannerNode {
     PlannerNode() = default;
     PlannerNode(PlannerNode const &src) = default;
 
-    static PlannerNode goal_node(WorldState goal) {
-        return PlannerNode{
-            goal, {}, {}
-        };
-    }
+    static PlannerNode goal_node(WorldState const &goal);
 
-    PlannerNode new_node_along(Ref<Action> action) const {
-        PlannerNode new_node{
-            action->prerequisites,
-            action->effects,
-            action,
-        };
-        for(WorldProperty const &prop : this->state)
-            new_node.state.insert(prop.key, prop.value);
-        for(WorldProperty const &prop : this->open_requirements)
-            new_node.open_requirements.insert(prop.key, prop.value);
-        return new_node;
-    }
+    PlannerNode new_node_along(Ref<Action> action) const;
 };
 
 class Planner : public Node {