diff --git a/public/assets/sign.png b/public/assets/sign.png
new file mode 100644
index 0000000..a778b3b
Binary files /dev/null and b/public/assets/sign.png differ
diff --git a/src/components/GameCanvas.tsx b/src/components/GameCanvas.tsx
index b6c585d..18dd52e 100644
--- a/src/components/GameCanvas.tsx
+++ b/src/components/GameCanvas.tsx
@@ -11,7 +11,7 @@ export interface GameCanvasProps {
 export const GameCanvas = ({ width, height }: GameCanvasProps) => {
   const canvasRef = useRef<HTMLCanvasElement>(null);
   const [game, setGame] = useState<TheAbstractionEngine>();
-  const [ready, setReady] = useState(false);
+  const [ready, setReady] = useState(true); // false);
   const [loading, setLoading] = useState(true);
 
   useEffect(() => {
diff --git a/src/engine/TheAbstractionEngine.ts b/src/engine/TheAbstractionEngine.ts
index 2c29406..4a0effa 100644
--- a/src/engine/TheAbstractionEngine.ts
+++ b/src/engine/TheAbstractionEngine.ts
@@ -33,7 +33,7 @@ export class TheAbstractionEngine {
     const facingDirectionSystem = new FacingDirection(inputSystem);
 
     [
-      new Level(LevelNames.LevelSelection),
+      new Level(LevelNames.Tutorial),
       inputSystem,
       facingDirectionSystem,
       new Grid(
diff --git a/src/engine/config/sprites.ts b/src/engine/config/sprites.ts
index f8912d5..481dbb9 100644
--- a/src/engine/config/sprites.ts
+++ b/src/engine/config/sprites.ts
@@ -11,6 +11,7 @@ export enum Sprites {
   BUBBLE,
   PORTAL,
   GRASS,
+  SIGN,
 }
 
 export interface SpriteSpec {
@@ -126,3 +127,12 @@ const grassSpriteSpec = {
   sheet: "/assets/grass.png",
 };
 SPRITE_SPECS.set(Sprites.GRASS, grassSpriteSpec);
+
+const signSpriteSpec = {
+  msPerFrame: 200,
+  width: 64,
+  height: 64,
+  frames: 3,
+  sheet: "/assets/sign.png",
+};
+SPRITE_SPECS.set(Sprites.SIGN, signSpriteSpec);
diff --git a/src/engine/entities/EntityNames.ts b/src/engine/entities/EntityNames.ts
index b4fbbb2..17b5519 100644
--- a/src/engine/entities/EntityNames.ts
+++ b/src/engine/entities/EntityNames.ts
@@ -10,4 +10,5 @@ export namespace EntityNames {
   export const Particles = "Particles";
   export const Portal = "Portal";
   export const Grass = "Grass";
+  export const Sign = "Sign";
 }
diff --git a/src/engine/entities/FunctionApplication.ts b/src/engine/entities/FunctionApplication.ts
index d907eca..175534c 100644
--- a/src/engine/entities/FunctionApplication.ts
+++ b/src/engine/entities/FunctionApplication.ts
@@ -34,6 +34,10 @@ import {
   interpret,
 } from "../../interpreter";
 
+const APPLICATION_RESULTS: Record<string, (gridPosition: Coord2D) => Entity> = {
+  _KEY: (gridPosition: Coord2D) => new Key(gridPosition),
+};
+
 export class FunctionApplication extends Entity {
   private static spriteSpec = SPRITE_SPECS.get(Sprites.BUBBLE) as SpriteSpec;
 
@@ -43,7 +47,9 @@ export class FunctionApplication extends Entity {
     super(EntityNames.FunctionApplication);
 
     this.symbolTable = new SymbolTable();
-    this.symbolTable.add("key");
+    Object.keys(APPLICATION_RESULTS).forEach((key) => {
+      this.symbolTable.add(key);
+    });
 
     const dimension = {
       width: FunctionApplication.spriteSpec.width,
@@ -109,9 +115,10 @@ export class FunctionApplication extends Entity {
       ComponentNames.LambdaTerm
     );
     const newCode = applicationTerm.code.replace("_INPUT", functionTerm.code);
+
     let result: DebrujinifiedLambdaTerm | null = null;
     try {
-      result = interpret(newCode, this.symbolTable);
+      result = interpret(newCode, this.symbolTable, true);
     } catch (e) {
       console.error(e);
       fail();
@@ -131,8 +138,9 @@ export class FunctionApplication extends Entity {
       applicationResultingEntity = new FunctionBox(grid.gridPosition, code);
     } else if ("name" in result) {
       const { name } = result;
-      if (name === "key") {
-        applicationResultingEntity = new Key(grid.gridPosition);
+      const entityFactory = APPLICATION_RESULTS[name];
+      if (entityFactory) {
+        game.addEntity(entityFactory(nextPosition));
       }
     } else {
       fail();
diff --git a/src/engine/entities/FunctionBox.ts b/src/engine/entities/FunctionBox.ts
index dac2174..7b70567 100644
--- a/src/engine/entities/FunctionBox.ts
+++ b/src/engine/entities/FunctionBox.ts
@@ -67,7 +67,10 @@ export class FunctionBox extends Entity {
   }
 }
 
-export const makeLambdaTermHighlightComponent = (entity: Entity) => {
+export const makeLambdaTermHighlightComponent = (
+  entity: Entity,
+  text?: string
+) => {
   const onUnhighlight = () => {
     closeModal();
     entity.removeComponent(ComponentNames.Interactable);
@@ -87,9 +90,9 @@ export const makeLambdaTermHighlightComponent = (entity: Entity) => {
         return;
       }
 
-      const code = entity.getComponent<LambdaTerm>(
-        ComponentNames.LambdaTerm
-      )!.code;
+      const code =
+        text ??
+        entity.getComponent<LambdaTerm>(ComponentNames.LambdaTerm)!.code;
       openModal(
         `<div style="text-align:center"><p>${code}</p> <br> <button id="close">Close</button></div>`
       );
diff --git a/src/engine/entities/Sign.ts b/src/engine/entities/Sign.ts
new file mode 100644
index 0000000..a11fba6
--- /dev/null
+++ b/src/engine/entities/Sign.ts
@@ -0,0 +1,49 @@
+import { Entity, EntityNames, makeLambdaTermHighlightComponent } from ".";
+import { BoundingBox, Colliding, Grid, Sprite } from "../components";
+import { IMAGES, SPRITE_SPECS, SpriteSpec, Sprites } from "../config";
+import { Coord2D } from "../interfaces";
+
+export class Sign extends Entity {
+  private static spriteSpec: SpriteSpec = SPRITE_SPECS.get(
+    Sprites.SIGN
+  ) as SpriteSpec;
+
+  private text: string;
+
+  constructor(text: string, gridPosition: Coord2D) {
+    super(EntityNames.Sign);
+    this.text = text;
+
+    const dimension = {
+      width: Sign.spriteSpec.width,
+      height: Sign.spriteSpec.height,
+    };
+
+    this.addComponent(
+      new Sprite(
+        IMAGES.get(Sign.spriteSpec.sheet)!,
+        { x: 0, y: 0 },
+        dimension,
+        Sign.spriteSpec.msPerFrame,
+        Sign.spriteSpec.frames
+      )
+    );
+
+    this.addComponent(
+      new BoundingBox(
+        {
+          x: 0,
+          y: 0,
+        },
+        dimension,
+        0
+      )
+    );
+
+    this.addComponent(new Grid(gridPosition));
+
+    this.addComponent(new Colliding());
+
+    this.addComponent(makeLambdaTermHighlightComponent(this, this.text));
+  }
+}
diff --git a/src/engine/entities/index.ts b/src/engine/entities/index.ts
index 260db5b..284a2bd 100644
--- a/src/engine/entities/index.ts
+++ b/src/engine/entities/index.ts
@@ -11,3 +11,4 @@ export * from "./FunctionApplication";
 export * from "./Particles";
 export * from "./Portal";
 export * from "./Grass";
+export * from "./Sign";
diff --git a/src/engine/levels/Tutorial.ts b/src/engine/levels/Tutorial.ts
index 694c8ff..b720346 100644
--- a/src/engine/levels/Tutorial.ts
+++ b/src/engine/levels/Tutorial.ts
@@ -6,6 +6,7 @@ import {
   LambdaFactory,
   LockedDoor,
   Player,
+  Sign,
   Wall,
 } from "../entities";
 
@@ -16,14 +17,15 @@ export class Tutorial extends Level {
 
   public init(game: Game): void {
     const entities = [
-      new Player({ x: 2, y: 2 }),
+      new Sign("TODO: Explain entities", { x: 4, y: 3 }),
       new Wall({ x: 10, y: 9 }),
       new Wall({ x: 10, y: 11 }),
       new Wall({ x: 11, y: 10 }),
       new Curry({ x: 10, y: 10 }),
       new LockedDoor({ x: 9, y: 10 }),
       new LambdaFactory({ x: 6, y: 3 }, "// TODO: Remove line\n(λ (x) . x)", 3),
-      new FunctionApplication({ x: 6, y: 6 }, "(_INPUT key)"),
+      new FunctionApplication({ x: 6, y: 6 }, "(_INPUT _KEY)"),
+      new Player({ x: 2, y: 2 }),
     ];
 
     entities.forEach((entity) => game.addEntity(entity));
diff --git a/src/interpreter/PeggyParser.js b/src/interpreter/PeggyParser.js
index 121cf9d..f5376b3 100644
--- a/src/interpreter/PeggyParser.js
+++ b/src/interpreter/PeggyParser.js
@@ -215,7 +215,7 @@ export default (function () {
     var peg$c2 = ".";
     var peg$c3 = "\r\n";
 
-    var peg$r0 = /^[a-zA-Z0-9]/;
+    var peg$r0 = options.allowUnderscores ? /^[a-zA-Z0-9_]/ : /^[a-zA-Z0-9]/;
     var peg$r1 = /^[\\\u03BB]/;
     var peg$r2 = /^[\t-\n ]/;
 
diff --git a/src/interpreter/parser.ts b/src/interpreter/parser.ts
index 5e3be0f..930b953 100644
--- a/src/interpreter/parser.ts
+++ b/src/interpreter/parser.ts
@@ -30,6 +30,10 @@ export const isVariable = (term: LambdaTerm): term is Variable => {
   return typeof term === "string";
 };
 
-export const parse = (term: string, library = false) => {
-  return peggyParser.parse(term, { peg$library: library });
+export const parse = (
+  term: string,
+  allowUnderscores = false,
+  library = false
+) => {
+  return peggyParser.parse(term, { peg$library: library, allowUnderscores });
 };