diff --git a/src/astar.rs b/src/astar.rs
index f344771..31d7b22 100644
--- a/src/astar.rs
+++ b/src/astar.rs
@@ -96,19 +96,25 @@ where
     }
 }
 
-pub fn astar<G, F, H, K, Reroute>(
+pub trait AstarStrategy<G, K>
+where
+    G: IntoEdges + Visitable,
+    K: Measure + Copy,
+    G::NodeId: Eq + Hash,
+{
+    fn reroute(&mut self, node: G::NodeId, tracker: &PathTracker<G>) -> Option<K>;
+    fn edge_cost(&mut self, edge: G::EdgeRef) -> K;
+    fn estimate_cost(&mut self, node: G::NodeId) -> K;
+}
+
+pub fn astar<G, K>(
     graph: G,
     start: G::NodeId,
-    mut reroute: Reroute,
-    mut edge_cost: F,
-    mut estimate_cost: H,
+    strategy: &mut impl AstarStrategy<G, K>,
 ) -> Option<(K, Vec<G::NodeId>)>
 where
     G: IntoEdges + Visitable,
-    Reroute: FnMut(G::NodeId, &PathTracker<G>) -> Option<K>,
     G::NodeId: Eq + Hash,
-    F: FnMut(G::EdgeRef) -> K,
-    H: FnMut(G::NodeId) -> K,
     K: Measure + Copy,
 {
     let mut visit_next = BinaryHeap::new();
@@ -118,10 +124,10 @@ where
 
     let zero_score = K::default();
     scores.insert(start, zero_score);
-    visit_next.push(MinScored(estimate_cost(start), start));
+    visit_next.push(MinScored(strategy.estimate_cost(start), start));
 
     while let Some(MinScored(estimate_score, node)) = visit_next.pop() {
-        match reroute(node, &path_tracker) {
+        match strategy.reroute(node, &path_tracker) {
             None => {
                 let path = path_tracker.reconstruct_path_to(node);
                 let cost = scores[&node];
@@ -148,7 +154,7 @@ where
 
                 for edge in graph.edges(node) {
                     let next = edge.target();
-                    let next_score = node_score + route_cost + edge_cost(edge);
+                    let next_score = node_score + route_cost + strategy.edge_cost(edge);
 
                     match scores.entry(next) {
                         Occupied(mut entry) => {
@@ -165,7 +171,7 @@ where
                     }
 
                     path_tracker.set_predecessor(next, node);
-                    let next_estimate_score = next_score + estimate_cost(next);
+                    let next_estimate_score = next_score + strategy.estimate_cost(next);
                     visit_next.push(MinScored(next_estimate_score, next));
                 }
             }
diff --git a/src/router.rs b/src/router.rs
index d4b816c..71952b3 100644
--- a/src/router.rs
+++ b/src/router.rs
@@ -2,7 +2,7 @@ use geo::geometry::Point;
 use petgraph::visit::{EdgeRef, IntoEdgeReferences};
 use spade::InsertionError;
 
-use crate::astar::astar;
+use crate::astar::{astar, AstarStrategy, PathTracker};
 use crate::bow::Bow;
 use crate::draw::{Draw, Head};
 use crate::graph::{BendIndex, DotIndex, Ends, SegIndex, TaggedIndex};
@@ -11,8 +11,8 @@ use crate::guide::Guide;
 use crate::layout::Layout;
 
 use crate::math::Circle;
-use crate::mesh::{Mesh, VertexIndex};
-use crate::route::Route;
+use crate::mesh::{Mesh, MeshEdgeReference, VertexIndex};
+use crate::route::{Route, Trace};
 use crate::rules::{Conditions, Rules};
 use crate::segbend::Segbend;
 
@@ -21,6 +21,45 @@ pub struct Router {
     rules: Rules,
 }
 
+pub struct DefaultAstarStrategy<'a> {
+    route: Route<'a>,
+    trace: Trace,
+    to: VertexIndex,
+}
+
+impl<'a> DefaultAstarStrategy<'a> {
+    pub fn new(route: Route<'a>, trace: Trace, to: VertexIndex) -> Self {
+        Self { route, trace, to }
+    }
+}
+
+impl<'a> AstarStrategy<&Mesh, u64> for DefaultAstarStrategy<'a> {
+    fn reroute(&mut self, vertex: VertexIndex, tracker: &PathTracker<&Mesh>) -> Option<u64> {
+        let new_path = tracker.reconstruct_path_to(vertex);
+
+        if vertex == self.to {
+            self.route
+                .rework_path(&mut self.trace, &new_path[..new_path.len() - 1], 5.0)
+                .ok();
+            self.route
+                .finish(&mut self.trace, new_path[new_path.len() - 1], 5.0)
+                .ok();
+            None
+        } else {
+            self.route.rework_path(&mut self.trace, &new_path, 5.0).ok();
+            Some(0)
+        }
+    }
+
+    fn edge_cost(&mut self, edge: MeshEdgeReference) -> u64 {
+        1
+    }
+
+    fn estimate_cost(&mut self, vertex: VertexIndex) -> u64 {
+        0
+    }
+}
+
 impl Router {
     pub fn new() -> Self {
         Router {
@@ -37,29 +76,12 @@ impl Router {
         mesh.triangulate(&self.layout)?;
 
         let mut route = self.route(&mesh);
-        let mut trace = route.start(mesh.vertex(from));
+        let trace = route.start(mesh.vertex(from));
 
         let (_cost, path) = astar(
             &mesh,
             mesh.vertex(from),
-            |node, tracker| {
-                let new_path = tracker.reconstruct_path_to(node);
-
-                if node == mesh.vertex(to) {
-                    route
-                        .rework_path(&mut trace, &new_path[..new_path.len() - 1], 5.0)
-                        .ok();
-                    route
-                        .finish(&mut trace, new_path[new_path.len() - 1], 5.0)
-                        .ok();
-                    None
-                } else {
-                    route.rework_path(&mut trace, &new_path, 5.0).ok();
-                    Some(0)
-                }
-            },
-            |_edge| 1,
-            |_| 0,
+            &mut DefaultAstarStrategy::new(route, trace, mesh.vertex(to)),
         )
         .unwrap(); // TODO.
         Ok(())