level one (applications prototype finished!)

44 files changed, 575 insertions, 66 deletions

diff --git a/public/assets/bubble.png b/public/assets/bubble.png
index 62744b3..9c8b758 100644
--- a/public/assets/bubble.png
+++ b/public/assets/bubble.png
diff --git a/public/assets/key.png b/public/assets/key.png
index c6d07a4..23bada6 100644
--- a/public/assets/key.png
+++ b/public/assets/key.png
diff --git a/public/assets/locked_door.png b/public/assets/locked_door.png
index 4a90d84..7175ae4 100644
--- a/public/assets/locked_door.png
+++ b/public/assets/locked_door.png
diff --git a/public/assets/sound/failure.wav b/public/assets/sound/failure.wav
new file mode 100644
index 0000000..c7dbddc
--- /dev/null
+++ b/public/assets/sound/failure.wav
diff --git a/public/assets/sound/keyopen.wav b/public/assets/sound/keyopen.wav
new file mode 100644
index 0000000..bdc2d18
--- /dev/null
+++ b/public/assets/sound/keyopen.wav
diff --git a/public/assets/sound/lambda_save.wav b/public/assets/sound/lambda_save.wav
new file mode 100644
index 0000000..b08c015
--- /dev/null
+++ b/public/assets/sound/lambda_save.wav
diff --git a/public/assets/sound/lambda_transform.wav b/public/assets/sound/lambda_transform.wav
new file mode 100644
index 0000000..03a180a
--- /dev/null
+++ b/public/assets/sound/lambda_transform.wav
diff --git a/public/assets/sound/modal_close.wav b/public/assets/sound/modal_close.wav
new file mode 100644
index 0000000..fe978d2
--- /dev/null
+++ b/public/assets/sound/modal_close.wav
diff --git a/public/assets/sound/modal_open.wav b/public/assets/sound/modal_open.wav
new file mode 100644
index 0000000..f28b1c7
--- /dev/null
+++ b/public/assets/sound/modal_open.wav
diff --git a/public/assets/sound/move_1.wav b/public/assets/sound/move_1.wav
new file mode 100644
index 0000000..76949dd
--- /dev/null
+++ b/public/assets/sound/move_1.wav
diff --git a/public/assets/sound/move_2.wav b/public/assets/sound/move_2.wav
new file mode 100644
index 0000000..d69e5e5
--- /dev/null
+++ b/public/assets/sound/move_2.wav
diff --git a/public/assets/sound/move_3.wav b/public/assets/sound/move_3.wav
new file mode 100644
index 0000000..3ade3bc
--- /dev/null
+++ b/public/assets/sound/move_3.wav
diff --git a/public/assets/sound/move_4.wav b/public/assets/sound/move_4.wav
new file mode 100644
index 0000000..0407d8a
--- /dev/null
+++ b/public/assets/sound/move_4.wav
diff --git a/public/assets/sound/music/credits.txt b/public/assets/sound/music/credits.txt
new file mode 100644
index 0000000..0ac1440
--- /dev/null
+++ b/public/assets/sound/music/credits.txt
@@ -0,0 +1,20 @@
+Reverie by 
+Music promoted by https://www.chosic.com/free-music/all/
+Creative Commons CC BY 4.0
+https://creativecommons.org/licenses/by/4.0/
+
+Moonlight by Scott Buckley | www.scottbuckley.com.au
+Music promoted by https://www.chosic.com/free-music/all/
+Creative Commons CC BY 4.0
+https://creativecommons.org/licenses/by/4.0/
+
+Jul by Scott Buckley | www.scottbuckley.com.au
+Music promoted by https://www.chosic.com/free-music/all/
+Creative Commons Attribution 4.0 International (CC BY 4.0)
+https://creativecommons.org/licenses/by/4.0/
+
+A Kind Of Hope by Scott Buckley | www.scottbuckley.com.au
+Music promoted by https://www.chosic.com/free-music/all/
+Creative Commons CC BY 4.0
+https://creativecommons.org/licenses/by/4.0/
+
diff --git a/public/assets/sound/music/hope.mp3 b/public/assets/sound/music/hope.mp3
new file mode 100644
index 0000000..2a3501a
--- /dev/null
+++ b/public/assets/sound/music/hope.mp3
diff --git a/public/assets/sound/music/jul.mp3 b/public/assets/sound/music/jul.mp3
new file mode 100644
index 0000000..c87218c
--- /dev/null
+++ b/public/assets/sound/music/jul.mp3
diff --git a/public/assets/sound/music/moonlight.mp3 b/public/assets/sound/music/moonlight.mp3
new file mode 100644
index 0000000..f1c0294
--- /dev/null
+++ b/public/assets/sound/music/moonlight.mp3
diff --git a/public/assets/sound/music/reverie.mp3 b/public/assets/sound/music/reverie.mp3
new file mode 100644
index 0000000..e77af11
--- /dev/null
+++ b/public/assets/sound/music/reverie.mp3
diff --git a/src/App.tsx b/src/App.tsx
index 3f3f67d..295b01b 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -32,6 +32,10 @@ export const App = () => {
           | inspired by{" "}
           <a href="https://hempuli.com/baba/" target="_blank">
             baba is you
+          </a>{" "}
+          | music by{" "}
+          <a href="https://www.scottbuckley.com.au" target="_blank">
+            scott buckley
           </a>
         </span>
       </div>
diff --git a/src/components/GameCanvas.tsx b/src/components/GameCanvas.tsx
index 09351e3..b6c585d 100644
--- a/src/components/GameCanvas.tsx
+++ b/src/components/GameCanvas.tsx
@@ -1,6 +1,7 @@
 import { useState, useEffect, useRef } from "react";
 import { TheAbstractionEngine, Game } from "../engine";
 import { Miscellaneous } from "../engine/config";
+import { Title } from "./Title";
 
 export interface GameCanvasProps {
   width: number;
@@ -10,6 +11,8 @@ 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 [loading, setLoading] = useState(true);
 
   useEffect(() => {
     if (canvasRef.current && !game) {
@@ -21,25 +24,35 @@ export const GameCanvas = ({ width, height }: GameCanvasProps) => {
 
         theAbstractionEngine.init().then(() => {
           theAbstractionEngine.play();
-          setGame(theAbstractionEngine);
-
           canvas.focus();
+
+          setGame(theAbstractionEngine);
+          setLoading(false);
         });
 
         return () => theAbstractionEngine.stop();
       }
     }
-  }, [canvasRef]);
+  }, [canvasRef, ready]);
+
+  if (ready) {
+    return (
+      <div className="centered-game">
+        <canvas
+          id={Miscellaneous.CANVAS_ID}
+          tabIndex={1}
+          ref={canvasRef}
+          width={loading ? 50 : width}
+          height={loading ? 50 : height}
+        ></canvas>
+        {loading && <span className="loading">Loading...</span>}
+      </div>
+    );
+  }
 
   return (
     <div className="centered-game">
-      <canvas
-        id={Miscellaneous.CANVAS_ID}
-        tabIndex={1}
-        ref={canvasRef}
-        width={width}
-        height={height}
-      ></canvas>
+      <Title setReady={setReady} />
     </div>
   );
 };
diff --git a/src/components/Title.tsx b/src/components/Title.tsx
new file mode 100644
index 0000000..99c7584
--- /dev/null
+++ b/src/components/Title.tsx
@@ -0,0 +1,17 @@
+export interface TitleProps {
+  setReady: (ready: boolean) => void;
+}
+
+export const Title = ({ setReady }: TitleProps) => {
+  return (
+    <div style={{ textAlign: "center" }}>
+      <h1>the abstraction engine</h1>
+      <p>a game based on the lambda calculus</p>
+
+      <br />
+      <hr />
+      <br />
+      <button onClick={() => setReady(true)}>ready</button>
+    </div>
+  );
+};
diff --git a/src/css/style.css b/src/css/style.css
index 35fdc31..1b98555 100644
--- a/src/css/style.css
+++ b/src/css/style.css
@@ -12,7 +12,6 @@
   padding: 0;
   margin: 0;
   font-family: "scientifica", monospace;
-  transition: background 0.2s ease-in-out;
   font-smooth: never;
 }
 
@@ -21,10 +20,13 @@ body {
   margin: 0;
   width: 100%;
   height: 100%;
+  background: radial-gradient(ellipse at top, var(--bg), transparent),
+    radial-gradient(ellipse at left, var(--blue), transparent),
+    radial-gradient(ellipse at right, var(--purple), transparent),
+    radial-gradient(ellipse at bottom, var(--bg), transparent);
 }
 
 body {
-  background-color: var(--bg);
   color: var(--text);
 }
 
@@ -51,17 +53,20 @@ a:visited {
   justify-content: space-around;
   padding-top: 1rem;
   padding-bottom: 1rem;
+  border-bottom: 2px solid var(--yellow);
+  border-radius: 0.5rem;
 }
 
 .content {
-  border-top: 1px solid var(--yellow);
-  border-bottom: 1px solid var(--yellow);
   max-height: 90vh;
 }
 
 .footer {
+  border-top: 2px solid var(--yellow);
+  border-radius: 0.5rem;
   padding-top: 1rem;
   padding-bottom: 1rem;
+  text-align: center;
 }
 
 .nav {
@@ -88,12 +93,13 @@ a:visited {
 
 .centered-game canvas {
   display: block;
-  max-height: 90%;
+  max-height: 100%;
   width: auto;
   max-width: 100%;
   border: 1px solid var(--yellow);
   border-radius: 0.5rem;
-  margin: 0;
+  margin-bottom: 2rem;
+  background-color: var(--bg);
 }
 
 button {
diff --git a/src/engine/TheAbstractionEngine.ts b/src/engine/TheAbstractionEngine.ts
index 20ff6cc..93684ef 100644
--- a/src/engine/TheAbstractionEngine.ts
+++ b/src/engine/TheAbstractionEngine.ts
@@ -7,6 +7,7 @@ import {
   Key,
   LockedDoor,
   Curry,
+  FunctionApplication,
 } from "./entities";
 import {
   Grid,
@@ -16,6 +17,7 @@ import {
   Collision,
   GridSpawner,
   Life,
+  Music,
 } from "./systems";
 
 export class TheAbstractionEngine {
@@ -49,8 +51,9 @@ export class TheAbstractionEngine {
       ),
       new GridSpawner(),
       new Collision(),
-      new Render(this.ctx),
       new Life(),
+      new Music(),
+      new Render(this.ctx),
     ].forEach((system) => this.game.addSystem(system));
 
     const player = new Player();
@@ -70,6 +73,9 @@ export class TheAbstractionEngine {
 
     const curry = new Curry({ x: 9, y: 8 });
     this.game.addEntity(curry);
+
+    const application = new FunctionApplication({ x: 5, y: 5 }, "(_INPUT key)");
+    this.game.addEntity(application);
   }
 
   public play() {
diff --git a/src/engine/components/Grid.ts b/src/engine/components/Grid.ts
index a62cc7b..9fad5ce 100644
--- a/src/engine/components/Grid.ts
+++ b/src/engine/components/Grid.ts
@@ -6,6 +6,7 @@ export class Grid extends Component {
 
   public gridPosition: Coord2D;
   public movingDirection: Direction;
+  public previousDirection: Direction;
 
   constructor(position: Coord2D = { x: 0, y: 0 }) {
     super(ComponentNames.Grid);
@@ -13,5 +14,6 @@ export class Grid extends Component {
     this.initialized = false;
     this.gridPosition = position;
     this.movingDirection = Direction.NONE;
+    this.previousDirection = this.movingDirection;
   }
 }
diff --git a/src/engine/config/assets.ts b/src/engine/config/assets.ts
index 5ce13e8..fbfab2f 100644
--- a/src/engine/config/assets.ts
+++ b/src/engine/config/assets.ts
@@ -1,4 +1,5 @@
 import { type SpriteSpec, SPRITE_SPECS } from ".";
+import { SOUND_SPECS, SoundSpec } from "./sounds";
 
 export const FONT = new FontFace("scientifica", "url(/fonts/scientifica.ttf)");
 FONT.load().then((font) => {
@@ -6,6 +7,7 @@ FONT.load().then((font) => {
 });
 
 export const IMAGES = new Map<string, HTMLImageElement>();
+export const SOUNDS = new Map<string, HTMLAudioElement>();
 
 export const loadSpritesIntoImageElements = (
   spriteSpecs: Partial<SpriteSpec>[],
@@ -35,6 +37,45 @@ export const loadSpritesIntoImageElements = (
   return spritePromises;
 };
 
+export const loadSoundsIntoAudioElements = (
+  soundSpecs: SoundSpec[],
+): Promise<void>[] => {
+  const soundPromises: Promise<void>[] = [];
+
+  for (const soundSpec of soundSpecs) {
+    if (soundSpec.url) {
+      const promise = fetch(soundSpec.url)
+        .then((response) => response.blob())
+        .then((blob) => {
+          const audio = new Audio();
+          audio.src = URL.createObjectURL(blob);
+          audio.volume = soundSpec.volume ?? 1;
+
+          SOUNDS.set(soundSpec.name, audio);
+          return new Promise<void>((resolve, rej) => {
+            audio.oncanplaythrough = () => {
+              resolve();
+            };
+
+            audio.onerror = (e) => {
+              console.error(soundSpec);
+              rej(e);
+            };
+          });
+        });
+      soundPromises.push(promise);
+    }
+
+    if (soundSpec.states) {
+      soundPromises.push(
+        ...loadSoundsIntoAudioElements(Array.from(soundSpec.states.values())),
+      );
+    }
+  }
+
+  return soundPromises;
+};
+
 export const loadAssets = () =>
   Promise.all([
     ...loadSpritesIntoImageElements(
@@ -43,5 +84,5 @@ export const loadAssets = () =>
       ),
     ),
     FONT.load(),
-    // TODO: Sound
+    ...loadSoundsIntoAudioElements(Array.from(SOUND_SPECS.values())),
   ]);
diff --git a/src/engine/config/index.ts b/src/engine/config/index.ts
index a574965..9b69740 100644
--- a/src/engine/config/index.ts
+++ b/src/engine/config/index.ts
@@ -1,3 +1,4 @@
 export * from "./constants";
 export * from "./assets";
 export * from "./sprites";
+export * from "./sounds";
diff --git a/src/engine/config/sounds.ts b/src/engine/config/sounds.ts
new file mode 100644
index 0000000..b182c86
--- /dev/null
+++ b/src/engine/config/sounds.ts
@@ -0,0 +1,84 @@
+export type SoundSpec = {
+  name: string;
+  url?: string;
+  volume?: number;
+  states?: Map<string | number, SoundSpec>;
+};
+
+export const MovingSound: SoundSpec = {
+  name: "moving",
+  states: new Map([
+    [1, { name: "moving_1", url: "/assets/sound/move_1.wav" }],
+    //    [2, { name: "moving_2", url: "/assets/sound/move_2.wav" }],
+    //    [3, { name: "moving_3", url: "/assets/sound/move_3.wav" }],
+    [4, { name: "moving_4", url: "/assets/sound/move_4.wav" }],
+  ]),
+};
+
+export const LambdaTransformSound: SoundSpec = {
+  name: "lambdaTransform",
+  url: "/assets/sound/lambda_transform.wav",
+  volume: 0.3,
+};
+
+export const LambdaSave: SoundSpec = {
+  name: "lambdaSave",
+  url: "/assets/sound/lambda_save.wav",
+};
+
+export const Failure: SoundSpec = {
+  name: "failure",
+  url: "/assets/sound/failure.wav",
+  volume: 0.5,
+};
+
+export const ModalOpen: SoundSpec = {
+  name: "modalOpen",
+  url: "/assets/sound/modal_open.wav",
+  volume: 0.5,
+};
+
+export const ModalClose: SoundSpec = {
+  name: "modalClose",
+  url: "/assets/sound/modal_close.wav",
+  volume: 0.5,
+};
+
+export const KeyOpen: SoundSpec = {
+  name: "keyOpen",
+  url: "/assets/sound/keyopen.wav",
+};
+
+export const Music: SoundSpec = {
+  name: "music",
+  states: new Map([
+    [
+      "hope",
+      { name: "hope", url: "/assets/sound/music/hope.mp3", volume: 0.5 },
+    ],
+    ["jul", { name: "jul", url: "/assets/sound/music/jul.mp3", volume: 0.5 }],
+    [
+      "reverie",
+      { name: "reverie", url: "/assets/sound/music/reverie.mp3", volume: 0.5 },
+    ],
+    [
+      "moonlight",
+      {
+        name: "moonlight",
+        url: "/assets/sound/music/moonlight.mp3",
+        volume: 0.5,
+      },
+    ],
+  ]),
+};
+
+export const SOUND_SPECS: SoundSpec[] = [
+  MovingSound,
+  LambdaTransformSound,
+  LambdaSave,
+  Failure,
+  ModalOpen,
+  ModalClose,
+  KeyOpen,
+  Music,
+];
diff --git a/src/engine/config/sprites.ts b/src/engine/config/sprites.ts
index cca5961..83bf0a0 100644
--- a/src/engine/config/sprites.ts
+++ b/src/engine/config/sprites.ts
@@ -8,6 +8,7 @@ export enum Sprites {
   KEY,
   LOCKED_DOOR,
   CURRY,
+  BUBBLE,
 }
 
 export interface SpriteSpec {
@@ -96,3 +97,12 @@ const currySpriteSpec = {
   sheet: "/assets/curry.png",
 };
 SPRITE_SPECS.set(Sprites.CURRY, currySpriteSpec);
+
+const bubbleSpriteSpec = {
+  msPerFrame: 200,
+  width: 64,
+  height: 64,
+  frames: 3,
+  sheet: "/assets/bubble.png",
+};
+SPRITE_SPECS.set(Sprites.BUBBLE, bubbleSpriteSpec);
diff --git a/src/engine/entities/FunctionApplication.ts b/src/engine/entities/FunctionApplication.ts
index 31e3490..24e4eec 100644
--- a/src/engine/entities/FunctionApplication.ts
+++ b/src/engine/entities/FunctionApplication.ts
@@ -1,7 +1,183 @@
-import { Entity, EntityNames } from ".";
+import {
+  Entity,
+  EntityNames,
+  FunctionBox,
+  Key,
+  Particles,
+  makeLambdaTermHighlightComponent,
+} from ".";
+import {
+  BoundingBox,
+  Colliding,
+  ComponentNames,
+  Grid,
+  LambdaTerm,
+  Sprite,
+} from "../components";
+import {
+  Failure,
+  IMAGES,
+  LambdaTransformSound,
+  SOUNDS,
+  SPRITE_SPECS,
+  SpriteSpec,
+  Sprites,
+} from "../config";
+import { Coord2D, Direction } from "../interfaces";
+import { Game } from "..";
+import { Grid as GridSystem, SystemNames } from "../systems";
+import { colors } from "../utils";
+import {
+  DebrujinifiedLambdaTerm,
+  SymbolTable,
+  emitNamed,
+  interpret,
+} from "../../interpreter";
 
 export class FunctionApplication extends Entity {
-  constructor() {
+  private static spriteSpec = SPRITE_SPECS.get(Sprites.BUBBLE) as SpriteSpec;
+
+  private symbolTable: SymbolTable;
+
+  constructor(gridPosition: Coord2D, lambdaTerm: string) {
     super(EntityNames.FunctionApplication);
+
+    this.symbolTable = new SymbolTable();
+    this.symbolTable.add("key");
+
+    const dimension = {
+      width: FunctionApplication.spriteSpec.width,
+      height: FunctionApplication.spriteSpec.height,
+    };
+    this.addComponent(
+      new BoundingBox(
+        {
+          x: 0,
+          y: 0,
+        },
+        dimension,
+        0,
+      ),
+    );
+
+    this.addComponent(new Grid(gridPosition));
+
+    this.addComponent(new LambdaTerm(lambdaTerm));
+
+    this.addComponent(
+      new Sprite(
+        IMAGES.get(FunctionApplication.spriteSpec.sheet)!,
+        { x: 0, y: 0 },
+        dimension,
+        FunctionApplication.spriteSpec.msPerFrame,
+        FunctionApplication.spriteSpec.frames,
+      ),
+    );
+
+    this.addComponent(new Colliding(this.handleCollision.bind(this)));
+
+    this.addComponent(makeLambdaTermHighlightComponent(this));
+  }
+
+  public handleCollision(game: Game, entity: Entity) {
+    if (entity.name !== EntityNames.FunctionBox) {
+      return;
+    }
+
+    const entityGrid = entity.getComponent<Grid>(ComponentNames.Grid);
+    if (entityGrid.movingDirection !== Direction.NONE) {
+      // prevent recursive functionBox -> application creation
+      return;
+    }
+
+    const grid = this.getComponent<Grid>(ComponentNames.Grid);
+    const gridSystem = game.getSystem<GridSystem>(SystemNames.Grid);
+    const fail = () => {
+      entityGrid.movingDirection = gridSystem.oppositeDirection(
+        entityGrid.previousDirection,
+      );
+      entity.addComponent(entityGrid);
+
+      const failureSound = SOUNDS.get(Failure.name)!;
+      failureSound.play();
+    };
+
+    const applicationTerm = this.getComponent<LambdaTerm>(
+      ComponentNames.LambdaTerm,
+    );
+    const functionTerm = entity.getComponent<LambdaTerm>(
+      ComponentNames.LambdaTerm,
+    );
+    const newCode = applicationTerm.code.replace("_INPUT", functionTerm.code);
+    let result: DebrujinifiedLambdaTerm | null = null;
+    try {
+      result = interpret(newCode, this.symbolTable);
+    } catch (e) {
+      console.error(e);
+      fail();
+      return;
+    }
+
+    const { dimension } = gridSystem;
+    const nextPosition = gridSystem.getNewGridPosition(
+      grid.gridPosition,
+      entityGrid.previousDirection,
+    );
+
+    let applicationResultingEntity: Entity | null = null; // this should be its own function
+    if ("abstraction" in result) {
+      const code = emitNamed(result);
+
+      applicationResultingEntity = new FunctionBox(grid.gridPosition, code);
+    } else if ("name" in result) {
+      const { name } = result;
+      if (name === "key") {
+        applicationResultingEntity = new Key(grid.gridPosition);
+      }
+    } else {
+      fail();
+      return;
+    }
+
+    game.removeEntity(entity.id);
+    if (applicationResultingEntity) {
+      const grid = applicationResultingEntity.getComponent<Grid>(
+        ComponentNames.Grid,
+      );
+      grid.movingDirection = entityGrid.previousDirection;
+      applicationResultingEntity.addComponent(grid);
+
+      game.addEntity(applicationResultingEntity);
+    }
+
+    this.playTransformSound();
+    const particles = new Particles({
+      center: gridSystem.gridToScreenPosition(nextPosition),
+      spawnerDimensions: {
+        width: dimension.width / 2,
+        height: dimension.height / 2,
+      },
+      particleCount: 10,
+      spawnerShape: "circle",
+      particleShape: "circle",
+      particleMeanSpeed: 0.25,
+      particleSpeedVariance: 0.15,
+      particleMeanLife: 150,
+      particleMeanSize: 2,
+      particleSizeVariance: 1,
+      particleLifeVariance: 20,
+      particleColors: [
+        colors.lightAqua,
+        colors.blue,
+        colors.green,
+        colors.lightGreen,
+      ],
+    });
+    game.addEntity(particles);
+  }
+
+  private playTransformSound() {
+    const audio = SOUNDS.get(LambdaTransformSound.name)!;
+    audio.play();
   }
 }
diff --git a/src/engine/entities/FunctionBox.ts b/src/engine/entities/FunctionBox.ts
index 92f1908..0c9123e 100644
--- a/src/engine/entities/FunctionBox.ts
+++ b/src/engine/entities/FunctionBox.ts
@@ -1,6 +1,9 @@
 import {
   IMAGES,
   Miscellaneous,
+  ModalClose,
+  ModalOpen,
+  SOUNDS,
   SPRITE_SPECS,
   SpriteSpec,
   Sprites,
@@ -72,10 +75,15 @@ export const makeLambdaTermHighlightComponent = (entity: Entity) => {
 
   const onHighlight = () => {
     let modalOpen = false;
+    const doModalClose = () => {
+      SOUNDS.get(ModalClose.name)!.play();
+      modalOpen = false;
+      closeModal();
+    };
+
     const interaction = () => {
       if (modalOpen) {
-        modalOpen = false;
-        closeModal();
+        doModalClose();
         return;
       }
 
@@ -86,9 +94,10 @@ export const makeLambdaTermHighlightComponent = (entity: Entity) => {
         `<div style="text-align:center"><p>${code}</p> <br> <button id="close">Close</button></div>`,
       );
       modalOpen = true;
+      SOUNDS.get(ModalOpen.name)!.play();
 
       document.getElementById("close")!.addEventListener("click", () => {
-        closeModal();
+        doModalClose();
         document.getElementById(Miscellaneous.CANVAS_ID)!.focus();
       });
     };
diff --git a/src/engine/entities/LambdaFactory.ts b/src/engine/entities/LambdaFactory.ts
index a0f5749..9ad1398 100644
--- a/src/engine/entities/LambdaFactory.ts
+++ b/src/engine/entities/LambdaFactory.ts
@@ -1,6 +1,11 @@
 import {
+  Failure,
   IMAGES,
+  LambdaSave,
+  LambdaTransformSound,
   Miscellaneous,
+  ModalOpen,
+  SOUNDS,
   SPRITE_SPECS,
   SpriteSpec,
   Sprites,
@@ -144,6 +149,8 @@ export class LambdaFactory extends Entity {
     const text = this.getComponent<Text>(ComponentNames.Text);
     text.text = spawner.spawnsLeft.toString();
     this.addComponent(text);
+
+    SOUNDS.get(LambdaTransformSound.name)!.play();
   }
 
   private openCodeEditor() {
@@ -185,6 +192,8 @@ export class LambdaFactory extends Entity {
       canvas,
       closeButton,
     };
+
+    SOUNDS.get(ModalOpen.name)!.play();
   }
 
   private refreshCodeEditorText(text: string) {
@@ -239,6 +248,7 @@ export class LambdaFactory extends Entity {
       });
 
       syntaxError.innerText = e.message;
+      SOUNDS.get(Failure.name)!.play();
       return;
     }
 
@@ -250,6 +260,7 @@ export class LambdaFactory extends Entity {
     closeModal();
 
     canvas.focus();
+    SOUNDS.get(LambdaSave.name)!.play();
   }
 
   private onHighlight(direction: Direction) {
diff --git a/src/engine/entities/LockedDoor.ts b/src/engine/entities/LockedDoor.ts
index b4887d6..aa1f328 100644
--- a/src/engine/entities/LockedDoor.ts
+++ b/src/engine/entities/LockedDoor.ts
@@ -7,7 +7,14 @@ import {
   Sprite,
   ComponentNames,
 } from "../components";
-import { IMAGES, SPRITE_SPECS, SpriteSpec, Sprites } from "../config";
+import {
+  IMAGES,
+  KeyOpen,
+  SOUNDS,
+  SPRITE_SPECS,
+  SpriteSpec,
+  Sprites,
+} from "../config";
 import { Coord2D } from "../interfaces";
 import { Grid as GridSystem, SystemNames } from "../systems";
 import { colors } from "../utils";
@@ -82,5 +89,12 @@ export class LockedDoor extends Entity {
     });
 
     game.addEntity(particles);
+
+    this.playKeySound();
+  }
+
+  private playKeySound() {
+    const audio = SOUNDS.get(KeyOpen.name)!;
+    audio.play();
   }
 }
diff --git a/src/engine/entities/Particles.ts b/src/engine/entities/Particles.ts
index 34b475c..5381b23 100644
--- a/src/engine/entities/Particles.ts
+++ b/src/engine/entities/Particles.ts
@@ -156,8 +156,12 @@ export class Particles extends Entity {
         Math.floor(Math.random() * options.particleColors.length)
       ];
     const position = {
-      x: options.center.x + Math.cos(angle) * options.spawnerDimensions.width,
-      y: options.center.y + Math.sin(angle) * options.spawnerDimensions.height,
+      x:
+        options.center.x +
+        (Math.cos(angle) * options.spawnerDimensions.width) / 2,
+      y:
+        options.center.y +
+        (Math.sin(angle) * options.spawnerDimensions.height) / 2,
     };
     if (options.spawnerShape === "rectangle") {
       // determine a random position on the edge of the spawner based on the angle
diff --git a/src/engine/entities/Player.ts b/src/engine/entities/Player.ts
index cb9161b..1b98383 100644
--- a/src/engine/entities/Player.ts
+++ b/src/engine/entities/Player.ts
@@ -6,6 +6,7 @@ import {
   Grid,
   BoundingBox,
   Control,
+  Pushable,
 } from "../components";
 import { Direction } from "../interfaces/";
 
@@ -28,6 +29,8 @@ export class Player extends Entity {
       ),
     );
 
+    this.addComponent(new Pushable());
+
     this.addComponent(new Control());
 
     this.addComponent(new Grid());
diff --git a/src/engine/systems/Collision.ts b/src/engine/systems/Collision.ts
index 8ef8215..7d843cc 100644
--- a/src/engine/systems/Collision.ts
+++ b/src/engine/systems/Collision.ts
@@ -6,6 +6,7 @@ import { BoundingBox, Colliding, ComponentNames, Grid } from "../components";
 const collisionMap: Record<string, Set<string>> = {
   [EntityNames.Key]: new Set([EntityNames.LockedDoor]),
   [EntityNames.Curry]: new Set([EntityNames.Player]),
+  [EntityNames.FunctionApplication]: new Set([EntityNames.FunctionBox]),
 };
 
 export class Collision extends System {
diff --git a/src/engine/systems/Grid.ts b/src/engine/systems/Grid.ts
index 1d4a623..9ab28e3 100644
--- a/src/engine/systems/Grid.ts
+++ b/src/engine/systems/Grid.ts
@@ -33,8 +33,8 @@ export class Grid extends System {
     this.rebuildGrid(game);
 
     this.highlightEntitiesLookedAt(game);
-    this.propogateEntityMovements(game);
 
+    this.propogateEntityMovements(game);
     this.updateMovingEntities(dt, game);
   }
 
@@ -209,9 +209,11 @@ export class Grid extends System {
   ) {
     game.forEachEntityWithComponent(ComponentNames.Grid, (entity) => {
       const grid = entity.getComponent<GridComponent>(ComponentNames.Grid)!;
+
       if (grid.movingDirection === Direction.NONE) {
         return;
       }
+      grid.previousDirection = grid.movingDirection;
 
       const boundingBox = entity.getComponent<BoundingBox>(
         ComponentNames.BoundingBox,
@@ -270,7 +272,7 @@ export class Grid extends System {
     });
   }
 
-  private getNewGridPosition(prev: Coord2D, direction: Direction) {
+  public getNewGridPosition(prev: Coord2D, direction: Direction) {
     let { x: newX, y: newY } = prev;
     switch (direction) {
       case Direction.LEFT:
@@ -290,6 +292,25 @@ export class Grid extends System {
     return { x: newX, y: newY };
   }
 
+  public oppositeDirection(direction: Direction) {
+    let opposite = Direction.NONE;
+    switch (direction) {
+      case Direction.LEFT:
+        opposite = Direction.RIGHT;
+        break;
+      case Direction.RIGHT:
+        opposite = Direction.LEFT;
+        break;
+      case Direction.UP:
+        opposite = Direction.DOWN;
+        break;
+      case Direction.DOWN:
+        opposite = Direction.UP;
+        break;
+    }
+    return opposite;
+  }
+
   private isEntityPastCenterWhenMoving(
     direction: Direction,
     gridPosition: Coord2D,
diff --git a/src/engine/systems/Input.ts b/src/engine/systems/Input.ts
index 8900f4e..c527f29 100644
--- a/src/engine/systems/Input.ts
+++ b/src/engine/systems/Input.ts
@@ -2,7 +2,7 @@ import { Grid as GridSystem, SystemNames, System } from ".";
 import { Game } from "..";
 import { ComponentNames, Grid, Interactable } from "../components";
 import { Control } from "../components/Control";
-import { Action, KeyConstants } from "../config";
+import { Action, KeyConstants, MovingSound, SOUNDS } from "../config";
 import { Entity, Particles } from "../entities";
 import { Coord2D, Direction } from "../interfaces";
 import { colors } from "../utils";
@@ -105,27 +105,44 @@ export class Input extends System {
     }
 
     if (moveUp || moveLeft || moveRight || moveDown) {
-      const gridPosition = gridComponent.gridPosition;
-      const gridSystem = game.getSystem<GridSystem>(SystemNames.Grid);
-      const particles = new Particles({
-        center: gridSystem.gridToScreenPosition(gridPosition),
-        particleCount: 5,
-        particleShape: "circle",
-        particleMeanSpeed: 0.05,
-        particleSpeedVariance: 0.005,
-        particleMeanLife: 120,
-        particleMeanSize: 5,
-        particleSizeVariance: 2,
-        particleLifeVariance: 30,
-        particleColors: [colors.gray, colors.darkGray],
-      });
-
-      game.addEntity(particles);
+      this.spawnParticlesAround(entity, game);
+      this.playMoveSound();
     }
 
     entity.addComponent(gridComponent);
   }
 
+  private playMoveSound() {
+    const movingSounds = Array.from(MovingSound.states!.values());
+    const soundName =
+      movingSounds[Math.floor(Math.random() * movingSounds.length)].name;
+    SOUNDS.get(soundName)!.play();
+  }
+
+  private spawnParticlesAround(entity: Entity, game: Game) {
+    const gridSystem = game.getSystem<GridSystem>(SystemNames.Grid);
+    const gridComponent = entity.getComponent<Grid>(ComponentNames.Grid)!;
+    const particles = new Particles({
+      center: gridSystem.gridToScreenPosition(gridComponent.gridPosition),
+      particleCount: 4,
+      spawnerShape: "circle",
+      spawnerDimensions: {
+        width: 10,
+        height: 10,
+      },
+      particleShape: "rectangle",
+      particleMeanSpeed: 0.05,
+      particleSpeedVariance: 0.005,
+      particleMeanLife: 120,
+      particleMeanSize: 3,
+      particleSizeVariance: 1,
+      particleLifeVariance: 30,
+      particleColors: [colors.gray, colors.darkGray, colors.lightPurple],
+    });
+
+    game.addEntity(particles);
+  }
+
   private hasSomeKey(keys?: string[]): boolean {
     if (keys) {
       return keys.some((key) => this.keys.has(key));
diff --git a/src/engine/systems/Music.ts b/src/engine/systems/Music.ts
new file mode 100644
index 0000000..6e2004d
--- /dev/null
+++ b/src/engine/systems/Music.ts
@@ -0,0 +1,40 @@
+import { System, SystemNames } from ".";
+import { Music as GameMusic, SOUNDS } from "../config";
+
+export class Music extends System {
+  private songs: string[] = [];
+  private currentSong?: string;
+
+  constructor() {
+    super(SystemNames.Music);
+
+    this.songs = Array.from(GameMusic.states!.values()).map(
+      (state) => state.name,
+    );
+  }
+
+  private chooseRandomSong() {
+    return this.songs[Math.floor(Math.random() * this.songs.length)];
+  }
+
+  public playNext() {
+    let nextSong = this.chooseRandomSong();
+    while (nextSong === this.currentSong) {
+      nextSong = this.chooseRandomSong();
+    }
+
+    this.currentSong = nextSong;
+    SOUNDS.get(this.currentSong)?.play();
+
+    // when done, play next song
+    SOUNDS.get(this.currentSong)?.addEventListener("ended", () => {
+      this.playNext();
+    });
+  }
+
+  public update(_dt: number) {
+    if (!this.currentSong) {
+      this.playNext();
+    }
+  }
+}
diff --git a/src/engine/systems/SystemNames.ts b/src/engine/systems/SystemNames.ts
index 738dfba..363c72c 100644
--- a/src/engine/systems/SystemNames.ts
+++ b/src/engine/systems/SystemNames.ts
@@ -6,4 +6,5 @@ export namespace SystemNames {
   export const GridSpawner = "GridSpawner";
   export const Collision = "Collision";
   export const Life = "Life";
+  export const Music = "Music";
 }
diff --git a/src/engine/systems/index.ts b/src/engine/systems/index.ts
index a420216..46c534d 100644
--- a/src/engine/systems/index.ts
+++ b/src/engine/systems/index.ts
@@ -7,3 +7,4 @@ export * from "./Grid";
 export * from "./GridSpawner";
 export * from "./Collision";
 export * from "./Life";
+export * from "./Music";
diff --git a/src/engine/utils/modal.ts b/src/engine/utils/modal.ts
index 48afae8..a378821 100644
--- a/src/engine/utils/modal.ts
+++ b/src/engine/utils/modal.ts
@@ -36,6 +36,6 @@ export const closeModal = (
       modal.style.display = "none";
 
       modalOpen = false;
-    }, 250);
+    }, 200);
   }
 };
diff --git a/src/interpreter/PeggyParser.js b/src/interpreter/PeggyParser.js
index 5671d91..632f1b7 100644
--- a/src/interpreter/PeggyParser.js
+++ b/src/interpreter/PeggyParser.js
@@ -201,7 +201,7 @@ export default (function () {
     );
   };
 
-  function peg$parse(input, options) {
+  function peg$parse(input, options, allowUnderscores = false) {
     options = options !== undefined ? options : {};
 
     var peg$FAILED = {};
@@ -215,7 +215,7 @@ export default (function () {
     var peg$c2 = ".";
     var peg$c3 = "\r\n";
 
-    var peg$r0 = /^[a-zA-Z0-9]/;
+    var peg$r0 = allowUnderscores ? /^[a-zA-Z0-9]_/ : /^[a-zA-Z0-9]/;
     var peg$r1 = /^[\\\u03BB]/;
     var peg$r2 = /^[\t-\n ]/;
 
diff --git a/src/interpreter/interpreter.ts b/src/interpreter/interpreter.ts
index 0b3ae34..4599c46 100644
--- a/src/interpreter/interpreter.ts
+++ b/src/interpreter/interpreter.ts
@@ -198,22 +198,6 @@ export const betaReduce = (
   );
 };
 
-export const interpret = (term: string): DebrujinifiedLambdaTerm => {
-  const ast = parse(term);
-  const symbolTable = new SymbolTable();
-  const debrujined = debrujinify(ast, symbolTable);
-
-  let prev = debrujined;
-  let next = betaReduce(prev);
-
-  while (emitDebrujin(prev) !== emitDebrujin(next)) {
-    // alpha equivalence
-    prev = next;
-    next = betaReduce(prev);
-  }
-  return next;
-};
-
 export const emitDebrujin = (term: DebrujinifiedLambdaTerm): string => {
   if ("index" in term) {
     return term.index.toString();
@@ -253,3 +237,22 @@ export const emitNamed = (term: DebrujinifiedLambdaTerm): string => {
 
   throw new InvalidLambdaTermError(`Invalid lambda term: ${term}`);
 };
+
+export const interpret = (
+  term: string,
+  symbolTable = new SymbolTable(),
+  allowUnderscores = false,
+): DebrujinifiedLambdaTerm => {
+  const ast = parse(term, allowUnderscores);
+  const debrujined = debrujinify(ast, symbolTable);
+
+  let prev = debrujined;
+  let next = betaReduce(prev);
+
+  while (emitDebrujin(prev) !== emitDebrujin(next)) {
+    // alpha equivalence
+    prev = next;
+    next = betaReduce(prev);
+  }
+  return next;
+};
diff --git a/src/interpreter/parser.ts b/src/interpreter/parser.ts
index 5e3be0f..d288815 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);
 };