5 files changed, 70 insertions, 8 deletions
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";