diff --git a/src/graph.js b/src/graph.js
index 6ee20ec..04b1e0e 100644
--- a/src/graph.js
+++ b/src/graph.js
@@ -56,7 +56,7 @@ export const reset_graph_view = (graph) => {
 
 export const highlight_node = (states, graph, current_state) => {
   graph.nodeColor((node) => {
-    if (states_are_equal(states[node.id], current_state)) {
+    if (states_are_equal(states.get(node.id), current_state)) {
       return "#FF0000";
     }
 
diff --git a/src/main.js b/src/main.js
index c77b615..1b6a695 100644
--- a/src/main.js
+++ b/src/main.js
@@ -26,14 +26,49 @@ let graph = null;
 // Helpers
 //
 
+export const key_of = (arr) => JSON.stringify(arr.board);
+
+const clear_states = () => {
+  states = {
+    _map: new Map(),
+
+    add(arr) {
+      const k = key_of(arr);
+      if (!this._map.has(k)) this._map.set(k, arr);
+      return this;
+    },
+
+    has(arr) {
+      return this._map.has(key_of(arr));
+    },
+
+    get(k) {
+      return this._map.get(k);
+    },
+
+    delete(arr) {
+      return this._map.delete(key_of(arr));
+    },
+
+    values() {
+      return [...this._map.values()];
+    },
+
+    get length() {
+      return this._map.size;
+    },
+  };
+};
+
 const clear_graph = () => {
   document.getElementById("graph").innerHTML = "";
   clear_visualization();
   model.visualize(initial_state);
-  states = [initial_state];
+  clear_states();
+  states.add(initial_state);
   current_state = initial_state;
   data = {
-    nodes: [{ id: 0 }],
+    nodes: [{ id: key_of(current_state) }],
     links: [],
   };
   graph = null;
@@ -61,9 +96,10 @@ window.onload = () => {
   document.getElementById("state_name").innerHTML = initial_state.name;
   clear_visualization();
   model.visualize(initial_state);
-  states = [initial_state];
+  clear_states();
+  states.add(initial_state);
   data = {
-    nodes: [{ id: 0 }],
+    nodes: [{ id: key_of(initial_state) }],
     links: [],
   };
   graph = generate_graph(data, node_click_view_state);
@@ -76,7 +112,7 @@ window.onload = () => {
 
 const node_click_view_state = (node, graph) => {
   clear_visualization();
-  current_state = states[node.id];
+  current_state = states.get(node.id);
 
   model.visualize(current_state);
   highlight_node(states, graph, current_state);
@@ -162,7 +198,8 @@ document.getElementById("select_model_button").addEventListener("click", () => {
   initial_state = model.initial_states[current_initial_state];
   selected_element = null;
   current_state = initial_state;
-  states = [initial_state];
+  clear_states();
+  states.add(initial_state);
   graph = null;
   graph = generate_graph(data, node_click_view_state);
   model.visualize(initial_state);
@@ -178,7 +215,8 @@ document.getElementById("select_state_button").addEventListener("click", () => {
   initial_state = model.initial_states[current_initial_state];
   current_state = initial_state;
   selected_element = null;
-  states = [initial_state];
+  clear_states();
+  states.add(initial_state);
   graph = null;
   graph = generate_graph(data, node_click_view_state);
   model.visualize(initial_state);
diff --git a/src/simulator/restricted_sliding_blocks/model.js b/src/simulator/restricted_sliding_blocks/model.js
index 63a4e53..52828f2 100644
--- a/src/simulator/restricted_sliding_blocks/model.js
+++ b/src/simulator/restricted_sliding_blocks/model.js
@@ -18,6 +18,7 @@ import {
 } from "./state.js";
 import { DIRECTIONS, LEFT, RIGHT, UP, DOWN } from "../../constants.js";
 import { HORIZONTAL, VERTICAL } from "../../constants.js";
+import { key_of } from "../../main.js";
 
 const initial_states = [
   single,
@@ -35,6 +36,8 @@ const generate = (states, initial_state, graph, previous_move) => {
 
   let last_print = 0;
 
+  let data = graph.graphData();
+
   while (stack.length > 0) {
     const [current_state, prev_move] = stack.pop();
 
@@ -45,7 +48,7 @@ const generate = (states, initial_state, graph, previous_move) => {
       const states_before = states.length;
       const [new_state, new_block] = move(
         states,
-        graph,
+        data,
         current_state,
         block,
         direction,
@@ -62,6 +65,8 @@ const generate = (states, initial_state, graph, previous_move) => {
       }
     }
   }
+
+  graph.graphData(data);
 };
 
 const select = (state, offsetX, offsetY) => {
@@ -84,7 +89,7 @@ const select = (state, offsetX, offsetY) => {
   return null;
 };
 
-const move = (states, graph, state, block, direction) => {
+const move = (states, data, state, block, direction) => {
   if (
     block[1] === HORIZONTAL &&
     (arrays_are_equal(direction, DIRECTIONS[UP]) ||
@@ -112,33 +117,29 @@ const move = (states, graph, state, block, direction) => {
   // insert_block(new_state, block);
 
   let new_state = structuredClone(state);
+  delete new_state.name;
   let new_block = move_block(block, direction);
   move_state_block(new_state, block, direction);
 
-  // TODO: Make states into a hashmap?
-  let index = index_of_state(states, new_state);
-
   let new_link = null;
   let new_node = null;
-  if (index !== null) {
+  if (states.has(new_state)) {
     // We already had this state, just generate a link
     new_link = {
-      source: index_of_state(states, state), // We're coming from this state...
-      target: index, // ...and ended up here, at a previous state.
+      source: key_of(state), // We're coming from this state...
+      target: key_of(new_state), // ...and ended up here, at a previous state.
     };
   } else {
-    states.push(new_state);
+    states.add(new_state);
     new_node = {
-      id: states.length - 1,
+      id: key_of(new_state),
     };
     new_link = {
-      source: index_of_state(states, state), // We're coming from this state...
-      target: states.length - 1, // ...and ended up here, at a new state.
+      source: key_of(state), // We're coming from this state...
+      target: key_of(new_state), // ...and ended up here, at a new state.
     };
   }
 
-  const data = graph.graphData();
-
   // TODO: Faster without this?
   const has_link = (data, link) => {
     // for (let l of data.links) {
@@ -154,15 +155,10 @@ const move = (states, graph, state, block, direction) => {
   };
 
   if (new_node !== null) {
-    graph.graphData({
-      nodes: [...data.nodes, new_node],
-      links: [...data.links, new_link],
-    });
+    data.nodes.push(new_node);
+    data.links.push(new_link);
   } else if (!has_link(data, new_link)) {
-    graph.graphData({
-      nodes: data.nodes,
-      links: [...data.links, new_link],
-    });
+    data.links.push(new_link);
   }
 
   return [new_state, new_block];
diff --git a/src/simulator/restricted_sliding_blocks/state.js b/src/simulator/restricted_sliding_blocks/state.js
index 95191f8..04ddba4 100644
--- a/src/simulator/restricted_sliding_blocks/state.js
+++ b/src/simulator/restricted_sliding_blocks/state.js
@@ -8,6 +8,7 @@ import {
   HORIZONTAL,
   VERTICAL,
 } from "../../constants.js";
+import { key_of } from "../../main.js";
 
 export const arrays_are_equal = (array, other_array) => {
   if (array.length != other_array.length) {
@@ -41,6 +42,8 @@ export const state_contains_block = (state, block) => {
 };
 
 export const states_are_equal = (state, other_state) => {
+  return key_of(state) === key_of(other_state);
+
   if (state.board.length != other_state.board.length) {
     return false;
   }
@@ -76,6 +79,7 @@ export const index_of_state = (states, state) => {
 
 export const remove_block = (state, block) => {
   let new_state = structuredClone(state);
+  delete new_state.name;
 
   new_state.board.splice(block[0], 1);
 
diff --git a/src/simulator/sliding_blocks/model.js b/src/simulator/sliding_blocks/model.js
index 069740c..3155898 100644
--- a/src/simulator/sliding_blocks/model.js
+++ b/src/simulator/sliding_blocks/model.js
@@ -13,6 +13,7 @@ import {
   insert_block,
   move_state_block,
 } from "./state.js";
+import { key_of } from "../../main.js";
 
 const initial_states = [single, two, three, four, small_klotski_like, klotski];
 
@@ -21,6 +22,8 @@ const generate = (states, initial_state, graph, previous_move) => {
 
   let last_print = 0;
 
+  let data = graph.graphData();
+
   while (stack.length > 0) {
     const [current_state, prev_move] = stack.pop();
 
@@ -31,7 +34,7 @@ const generate = (states, initial_state, graph, previous_move) => {
       const states_before = states.length;
       const [new_state, new_block] = move(
         states,
-        graph,
+        data,
         current_state,
         block,
         direction,
@@ -48,6 +51,8 @@ const generate = (states, initial_state, graph, previous_move) => {
       }
     }
   }
+
+  graph.graphData(data);
 };
 
 const select = (state, offsetX, offsetY) => {
@@ -70,7 +75,7 @@ const select = (state, offsetX, offsetY) => {
   return null;
 };
 
-const move = (states, graph, state, block, direction) => {
+const move = (states, data, state, block, direction) => {
   if (!block_is_movable(state, block, direction)) {
     return [null, null];
   }
@@ -82,6 +87,7 @@ const move = (states, graph, state, block, direction) => {
   let new_state;
   try {
     new_state = structuredClone(state);
+    delete new_state.name; // Only need this for the initial state
   } catch (e) {
     console.log(e);
     return [null, null];
@@ -89,30 +95,25 @@ const move = (states, graph, state, block, direction) => {
   let new_block = move_block(block, direction);
   move_state_block(new_state, block, direction);
 
-  // TODO: Make states into a hashmap?
-  let index = index_of_state(states, new_state);
-
   let new_link = null;
   let new_node = null;
-  if (index !== null) {
+  if (states.has(new_state)) {
     // We already had this state, just generate a link
     new_link = {
-      source: index_of_state(states, state), // We're coming from this state...
-      target: index, // ...and ended up here, at a previous state.
+      source: key_of(state), // We're coming from this state...
+      target: key_of(new_state), // ...and ended up here, at a previous state.
     };
   } else {
-    states.push(new_state);
+    states.add(new_state);
     new_node = {
-      id: states.length - 1,
+      id: key_of(new_state),
     };
     new_link = {
-      source: index_of_state(states, state), // We're coming from this state...
-      target: states.length - 1, // ...and ended up here, at a new state.
+      source: key_of(state), // We're coming from this state...
+      target: key_of(new_state), // ...and ended up here, at a new state.
     };
   }
 
-  const data = graph.graphData();
-
   // TODO: Faster without this?
   const has_link = (data, link) => {
     // for (let l of data.links) {
@@ -128,15 +129,10 @@ const move = (states, graph, state, block, direction) => {
   };
 
   if (new_node !== null) {
-    graph.graphData({
-      nodes: [...data.nodes, new_node],
-      links: [...data.links, new_link],
-    });
+    data.nodes.push(new_node);
+    data.links.push(new_link);
   } else if (!has_link(data, new_link)) {
-    graph.graphData({
-      nodes: data.nodes,
-      links: [...data.links, new_link],
-    });
+    data.links.push(new_link);
   }
 
   return [new_state, new_block];
diff --git a/src/simulator/sliding_blocks/state.js b/src/simulator/sliding_blocks/state.js
index e06518b..8f9828e 100644
--- a/src/simulator/sliding_blocks/state.js
+++ b/src/simulator/sliding_blocks/state.js
@@ -6,6 +6,7 @@ import {
   DIRECTIONS,
   invert_direction,
 } from "../../constants.js";
+import { key_of } from "../../main.js";
 
 export const arrays_are_equal = (array, other_array) => {
   if (array.length != other_array.length) {
@@ -39,6 +40,8 @@ export const state_contains_block = (state, block) => {
 };
 
 export const states_are_equal = (state, other_state) => {
+  return key_of(state) === key_of(other_state);
+
   if (state.board.length != other_state.board.length) {
     return false;
   }
@@ -74,6 +77,7 @@ export const index_of_state = (states, state) => {
 
 export const remove_block = (state, block) => {
   let new_state = structuredClone(state);
+  delete new_state.name;
 
   new_state.board.splice(block[0], 1);