diff --git a/src/css/modal.css b/src/css/modal.css
index bd6f2a3..a609ef9 100644
--- a/src/css/modal.css
+++ b/src/css/modal.css
@@ -1,32 +1,30 @@
-/* The Modal (background) */
 .modal {
-  display: none; /* Hidden by default */
-  position: fixed; /* Stay in place */
-  z-index: 1; /* Sit on top */
+  display: none;
+  position: fixed;
+  z-index: 1;
   left: 0;
   top: 0;
-  width: 100%; /* Full width */
-  height: 100%; /* Full height */
-  justify-content: center; /* Center horizontally */
-  align-items: center; /* Center vertically */
-  background-color: rgba(0, 0, 0, 0.4); /* Black w/ opacity */
-  overflow: auto; /* Enable scroll if needed */
-  animation: fadeIn 0.25s; /* Fade in the background */
+  width: 100%;
+  height: 100%;
+  justify-content: center;
+  align-items: center;
+  background-color: rgba(0, 0, 0, 0.4);
+  overflow: auto;
+  animation: fadeIn 0.25s;
 }
 
-/* Modal Content */
 .modal-content {
   display: flex;
-  background-color: #282828; /* Gruvbox background */
-  color: #ebdbb2; /* Gruvbox foreground */
+  background-color: #282828;
+  color: #ebdbb2;
   margin: auto;
   padding: 20px;
-  border: 1px solid #928374; /* Gruvbox grey */
-  width: 40%; /* Adjust as needed */
+  border: 1px solid #928374;
+  width: 40%;
   box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
-  animation: scaleUp 0.25s; /* Scale animation */
-  border-radius: 8px; /* Rounded corners */
-  justify-content: center; /* Center horizontally */
+  animation: scaleUp 0.25s;
+  border-radius: 8px;
+  justify-content: center;
 }
 
 /* Animations */
diff --git a/src/engine/TheAbstractionEngine.ts b/src/engine/TheAbstractionEngine.ts
index 15ef011..2db599b 100644
--- a/src/engine/TheAbstractionEngine.ts
+++ b/src/engine/TheAbstractionEngine.ts
@@ -1,8 +1,7 @@
 import { Game } from ".";
 import { Miscellaneous, loadAssets } from "./config";
-import { Player, FunctionBox } from "./entities";
-import { FacingDirection, Input, Render } from "./systems";
-import { Grid } from "./systems/Grid";
+import { Player, FunctionBox, Wall } from "./entities";
+import { Grid, FacingDirection, Input, Render } from "./systems";
 
 export class TheAbstractionEngine {
   private game: Game;
@@ -24,7 +23,6 @@ export class TheAbstractionEngine {
     const facingDirectionSystem = new FacingDirection(inputSystem);
 
     [
-      new Render(this.ctx),
       inputSystem,
       facingDirectionSystem,
       new Grid(
@@ -34,6 +32,7 @@ export class TheAbstractionEngine {
           height: Miscellaneous.GRID_CELL_HEIGHT,
         },
       ),
+      new Render(this.ctx),
     ].forEach((system) => this.game.addSystem(system));
 
     const player = new Player();
@@ -43,6 +42,9 @@ export class TheAbstractionEngine {
     this.game.addEntity(box);
     const box2 = new FunctionBox({ x: 4, y: 1 }, "λ x . (x)");
     this.game.addEntity(box2);
+
+    const wall = new Wall({ x: 5, y: 3 });
+    this.game.addEntity(wall);
   }
 
   public play() {
diff --git a/src/engine/components/Colliding.ts b/src/engine/components/Colliding.ts
new file mode 100644
index 0000000..4027c3d
--- /dev/null
+++ b/src/engine/components/Colliding.ts
@@ -0,0 +1,7 @@
+import { Component, ComponentNames } from ".";
+
+export class Colliding extends Component {
+  constructor() {
+    super(ComponentNames.Colliding);
+  }
+}
diff --git a/src/engine/components/ComponentNames.ts b/src/engine/components/ComponentNames.ts
index da6c37a..5e9b589 100644
--- a/src/engine/components/ComponentNames.ts
+++ b/src/engine/components/ComponentNames.ts
@@ -6,4 +6,6 @@ export namespace ComponentNames {
   export const Control = "Control";
   export const Highlight = "Highlight";
   export const Interactable = "Interactable";
+  export const Pushable = "Pushable";
+  export const Colliding = "Colliding";
 }
diff --git a/src/engine/components/Grid.ts b/src/engine/components/Grid.ts
index 0c18a65..a62cc7b 100644
--- a/src/engine/components/Grid.ts
+++ b/src/engine/components/Grid.ts
@@ -6,15 +6,12 @@ export class Grid extends Component {
 
   public gridPosition: Coord2D;
   public movingDirection: Direction;
-  public pushable: boolean = false;
 
-  constructor(pushable: boolean = false, position: Coord2D = { x: 0, y: 0 }) {
+  constructor(position: Coord2D = { x: 0, y: 0 }) {
     super(ComponentNames.Grid);
 
     this.initialized = false;
-
     this.gridPosition = position;
     this.movingDirection = Direction.NONE;
-    this.pushable = pushable;
   }
 }
diff --git a/src/engine/components/Highlight.ts b/src/engine/components/Highlight.ts
index 49d9f96..5875057 100644
--- a/src/engine/components/Highlight.ts
+++ b/src/engine/components/Highlight.ts
@@ -1,7 +1,33 @@
 import { Component, ComponentNames } from ".";
 
 export class Highlight extends Component {
-  constructor() {
+  public isHighlighted: boolean;
+  private onHighlight: Function;
+  private onUnhighlight: Function;
+
+  constructor(
+    onHighlight: Function,
+    onUnhighlight: Function,
+    isHighlighted: boolean = false,
+  ) {
     super(ComponentNames.Highlight);
+
+    this.isHighlighted = isHighlighted;
+    this.onHighlight = onHighlight;
+    this.onUnhighlight = onUnhighlight;
+  }
+
+  public highlight() {
+    if (!this.isHighlighted) {
+      this.isHighlighted = true;
+      this.onHighlight();
+    }
+  }
+
+  public unhighlight() {
+    if (this.isHighlighted) {
+      this.isHighlighted = false;
+      this.onUnhighlight();
+    }
   }
 }
diff --git a/src/engine/components/Pushable.ts b/src/engine/components/Pushable.ts
new file mode 100644
index 0000000..b3d0dc4
--- /dev/null
+++ b/src/engine/components/Pushable.ts
@@ -0,0 +1,11 @@
+import { Component, ComponentNames } from ".";
+
+export class Pushable extends Component {
+  public pushable: boolean;
+
+  constructor(pushable = false) {
+    super(ComponentNames.Pushable);
+
+    this.pushable = pushable;
+  }
+}
diff --git a/src/engine/components/index.ts b/src/engine/components/index.ts
index c470eff..4ae886a 100644
--- a/src/engine/components/index.ts
+++ b/src/engine/components/index.ts
@@ -7,3 +7,5 @@ export * from "./BoundingBox";
 export * from "./Control";
 export * from "./Highlight";
 export * from "./Interactable";
+export * from "./Pushable";
+export * from "./Colliding";
diff --git a/src/engine/config/sprites.ts b/src/engine/config/sprites.ts
index eab65fd..7cb8adf 100644
--- a/src/engine/config/sprites.ts
+++ b/src/engine/config/sprites.ts
@@ -3,6 +3,7 @@ import { Direction } from "../interfaces/Direction";
 export enum Sprites {
   PLAYER,
   FUNCTION_BOX,
+  WALL,
 }
 
 export interface SpriteSpec {
@@ -46,3 +47,12 @@ const functionBoxSpriteSpec = {
   sheet: "/assets/function_block.png",
 };
 SPRITE_SPECS.set(Sprites.FUNCTION_BOX, functionBoxSpriteSpec);
+
+const wallSpriteSpec = {
+  msPerFrame: 200,
+  width: 64,
+  height: 64,
+  frames: 3,
+  sheet: "/assets/wall.png",
+};
+SPRITE_SPECS.set(Sprites.WALL, wallSpriteSpec);
diff --git a/src/engine/entities/EntityNames.ts b/src/engine/entities/EntityNames.ts
index 1a4c1ed..ffcc937 100644
--- a/src/engine/entities/EntityNames.ts
+++ b/src/engine/entities/EntityNames.ts
@@ -1,4 +1,5 @@
 export namespace EntityNames {
   export const Player = "Player";
   export const FunctionBox = "FunctionBox";
+  export const Wall = "Wall";
 }
diff --git a/src/engine/entities/FunctionBox.ts b/src/engine/entities/FunctionBox.ts
index 57eeedb..e5d031a 100644
--- a/src/engine/entities/FunctionBox.ts
+++ b/src/engine/entities/FunctionBox.ts
@@ -4,7 +4,9 @@ import {
   BoundingBox,
   ComponentNames,
   Grid,
+  Highlight,
   Interactable,
+  Pushable,
   Sprite,
 } from "../components";
 import { Coord2D } from "../interfaces";
@@ -36,7 +38,9 @@ export class FunctionBox extends Entity {
       ),
     );
 
-    this.addComponent(new Grid(true, gridPosition));
+    this.addComponent(new Pushable());
+
+    this.addComponent(new Grid(gridPosition));
 
     this.addComponent(
       new Sprite(
@@ -51,25 +55,31 @@ export class FunctionBox extends Entity {
       ),
     );
 
-    this.hooks.set(ComponentNames.Highlight, {
-      add: () => {
-        let modalOpen = false;
-        const interaction = () => {
-          if (modalOpen) {
-            modalOpen = false;
-            closeModal();
-            return;
-          }
-          modalOpen = true;
-          openModal(this.code);
-        };
+    this.addComponent(
+      new Highlight(
+        () => this.onHighlight(),
+        () => this.onUnhighlight(),
+      ),
+    );
+  }
 
-        this.addComponent(new Interactable(interaction));
-      },
-      remove: () => {
+  private onUnhighlight() {
+    closeModal();
+    this.removeComponent(ComponentNames.Interactable);
+  }
+
+  private onHighlight() {
+    let modalOpen = false;
+    const interaction = () => {
+      if (modalOpen) {
+        modalOpen = false;
         closeModal();
-        this.removeComponent(ComponentNames.Interactable);
-      },
-    });
+        return;
+      }
+      modalOpen = true;
+      openModal(this.code);
+    };
+
+    this.addComponent(new Interactable(interaction));
   }
 }
diff --git a/src/engine/entities/Wall.ts b/src/engine/entities/Wall.ts
new file mode 100644
index 0000000..621a569
--- /dev/null
+++ b/src/engine/entities/Wall.ts
@@ -0,0 +1,45 @@
+import { Entity, EntityNames } from ".";
+import { BoundingBox, Colliding, Grid, Sprite } from "../components";
+import { IMAGES, SPRITE_SPECS, SpriteSpec, Sprites } from "../config";
+import { Coord2D } from "../interfaces";
+
+export class Wall extends Entity {
+  private static spriteSpec: SpriteSpec = SPRITE_SPECS.get(
+    Sprites.WALL,
+  ) as SpriteSpec;
+
+  constructor(gridPosition: Coord2D) {
+    super(EntityNames.Wall);
+
+    this.addComponent(new Grid(gridPosition));
+
+    this.addComponent(new Colliding());
+
+    this.addComponent(
+      new BoundingBox(
+        {
+          x: 0,
+          y: 0,
+        },
+        {
+          width: Wall.spriteSpec.width,
+          height: Wall.spriteSpec.height,
+        },
+        0,
+      ),
+    );
+
+    this.addComponent(
+      new Sprite(
+        IMAGES.get(Wall.spriteSpec.sheet)!,
+        { x: 0, y: 0 },
+        {
+          width: Wall.spriteSpec.width,
+          height: Wall.spriteSpec.height,
+        },
+        Wall.spriteSpec.msPerFrame,
+        Wall.spriteSpec.frames,
+      ),
+    );
+  }
+}
diff --git a/src/engine/entities/index.ts b/src/engine/entities/index.ts
index d6a8aed..e63b272 100644
--- a/src/engine/entities/index.ts
+++ b/src/engine/entities/index.ts
@@ -2,3 +2,4 @@ export * from "./Entity";
 export * from "./EntityNames";
 export * from "./Player";
 export * from "./FunctionBox";
+export * from "./Wall";
diff --git a/src/engine/systems/Grid.ts b/src/engine/systems/Grid.ts
index c9cab6b..28ca5ea 100644
--- a/src/engine/systems/Grid.ts
+++ b/src/engine/systems/Grid.ts
@@ -71,14 +71,20 @@ export class Grid extends System {
 
     highlightableEntities.forEach((id) => {
       const entity = game.getEntity(id)!;
-      if (!entity.hasComponent(ComponentNames.Highlight)) {
-        entity.addComponent(new Highlight());
+      if (entity.hasComponent(ComponentNames.Highlight)) {
+        const highlight = entity.getComponent<Highlight>(
+          ComponentNames.Highlight,
+        )!;
+        highlight.highlight();
       }
     });
 
     game.forEachEntityWithComponent(ComponentNames.Highlight, (entity) => {
       if (!highlightableEntities.has(entity.id)) {
-        entity.removeComponent(ComponentNames.Highlight);
+        const highlight = entity.getComponent<Highlight>(
+          ComponentNames.Highlight,
+        )!;
+        highlight.unhighlight();
       }
     });
   }
@@ -97,21 +103,41 @@ export class Grid extends System {
     // continue until no more pushable entities are found
     for (const entity of movingEntities) {
       const grid = entity.getComponent<GridComponent>(ComponentNames.Grid)!;
+      const { gridPosition, movingDirection } = grid;
+
+      grid.movingDirection = Direction.NONE;
+      entity.addComponent(grid); // default to not moving
+
       let nextGridPosition = this.getNewGridPosition(
-        grid.gridPosition,
-        grid.movingDirection,
+        gridPosition,
+        movingDirection,
       );
+
+      const moving = new Set<string>();
+      moving.add(entity.id);
+
       while (!this.isOutOfBounds(nextGridPosition)) {
         const { x, y } = nextGridPosition;
         const entities = Array.from(this.grid[y][x]).map(
           (id) => game.getEntity(id)!,
         );
 
+        if (
+          entities.some((entity) =>
+            entity.hasComponent(ComponentNames.Colliding),
+          )
+        ) {
+          moving.clear();
+          break;
+        }
+
         const pushableEntities = entities.filter((entity) => {
           if (!entity.hasComponent(ComponentNames.Grid)) return false;
 
-          const { pushable, movingDirection } =
-            entity.getComponent<GridComponent>(ComponentNames.Grid)!;
+          const { movingDirection } = entity.getComponent<GridComponent>(
+            ComponentNames.Grid,
+          )!;
+          const pushable = entity.hasComponent(ComponentNames.Pushable);
           return movingDirection === Direction.NONE && pushable;
         });
         if (pushableEntities.length === 0) {
@@ -119,18 +145,21 @@ export class Grid extends System {
         }
 
         for (const pushableEntity of pushableEntities) {
-          const pushableGrid = pushableEntity.getComponent<GridComponent>(
-            ComponentNames.Grid,
-          )!;
-          pushableGrid.movingDirection = grid.movingDirection;
-          pushableEntity.addComponent(pushableEntity);
+          moving.add(pushableEntity.id);
         }
 
         nextGridPosition = this.getNewGridPosition(
           nextGridPosition,
-          grid.movingDirection,
+          movingDirection,
         );
       }
+
+      for (const id of moving) {
+        const entity = game.getEntity(id)!;
+        const grid = entity.getComponent<GridComponent>(ComponentNames.Grid)!;
+        grid.movingDirection = movingDirection;
+        entity.addComponent(grid);
+      }
     }
   }
 
diff --git a/src/engine/systems/Render.ts b/src/engine/systems/Render.ts
index 7cb5d81..83daa52 100644
--- a/src/engine/systems/Render.ts
+++ b/src/engine/systems/Render.ts
@@ -1,5 +1,5 @@
 import { System, SystemNames } from ".";
-import { BoundingBox, ComponentNames, Sprite } from "../components";
+import { BoundingBox, ComponentNames, Highlight, Sprite } from "../components";
 import { Game } from "..";
 import { clamp } from "../utils";
 import { DrawArgs } from "../interfaces";
@@ -43,8 +43,13 @@ export class Render extends System {
         center: boundingBox.center,
         dimension: boundingBox.dimension,
         rotation: boundingBox.rotation,
-        tint: entity.hasComponent(ComponentNames.Highlight) ? "red" : undefined,
       };
+      if (entity.hasComponent(ComponentNames.Highlight)) {
+        const highlight = entity.getComponent<Highlight>(
+          ComponentNames.Highlight,
+        );
+        drawArgs.tint = highlight.isHighlighted ? "red" : undefined;
+      }
 
       sprite.draw(this.ctx, drawArgs);
     });
diff --git a/src/engine/systems/index.ts b/src/engine/systems/index.ts
index 31c98ac..18ffa2e 100644
--- a/src/engine/systems/index.ts
+++ b/src/engine/systems/index.ts
@@ -3,3 +3,4 @@ export * from "./System";
 export * from "./Render";
 export * from "./Input";
 export * from "./FacingDirection";
+export * from "./Grid";