10 files changed, 605 insertions, 0 deletions

diff --git a/Homework/cs5410/bbiy/src/systems/collision.js b/Homework/cs5410/bbiy/src/systems/collision.js
new file mode 100644
index 0000000..0732c74
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/collision.js
@@ -0,0 +1,93 @@
+game.system.Collision = (entitiesGrid) => {
+  const update = (elapsedTime, entities, changedIds) => {
+    const thisChangedIds = new Set();
+    for (let entity of Object.keys(entities).map((id) => entities[id])) {
+      if (entity.hasComponent("position") && entity.hasComponent("gridPosition") && (entity.hasComponent("burnable") || entity.hasComponent("sinkable")) && entity.hasComponent("alive")) {
+        for (let collided of entitiesGrid[entity.components.gridPosition.y][entity.components.gridPosition.x].values()) {
+          if (!equivalence(entity, collided) && collided.hasComponent("alive")){
+            if (entity.hasComponent("burnable") && collided.hasComponent("burn")) {
+              const burnedParticleSpawner = game.createBorderParticles({colors: ["#f58d42", "#d6600b", "#c7a312", "#f2b844"]});
+              burnedParticleSpawner.addComponent(game.components.Position(collided.components.position));
+              burnedParticleSpawner.addComponent(game.components.Appearance({width: game.canvas.width / game.config.xDim, height: game.canvas.height / game.config.yDim}));
+              game.entities[burnedParticleSpawner.id] = burnedParticleSpawner;
+              entity.removeComponent("alive");
+              game.assets.death.play();
+              break;
+            } else if (entity.hasComponent("sinkable") && collided.hasComponent("sink")) {
+              const sunkParticleSpawner = game.createBorderParticles({colors: ["#16f7c9", "#0d6e5a", "#2fa18a", "#48cfb4", "#58877d", "#178054", "#2cdb92"]});
+              sunkParticleSpawner.addComponent(game.components.Position(collided.components.position));
+              sunkParticleSpawner.addComponent(game.components.Appearance({width: game.canvas.width / game.config.xDim, height: game.canvas.height / game.config.yDim}));
+              game.entities[sunkParticleSpawner.id] = sunkParticleSpawner;
+              entity.removeComponent("alive");
+              collided.removeComponent("alive");
+              game.assets.death.play();
+              break;
+            }
+          }
+        }
+      }
+      if (entity.hasComponent("controllable") && entity.hasComponent("gridPosition")) {
+        for (let collided of entitiesGrid[entity.components.gridPosition.y][entity.components.gridPosition.x].values()) {
+          if (collided.hasComponent("win")) {
+            game.assets.win.play();
+            game.win = true;
+            game.systems.menu.bringUpMenu();
+            game.systems.menu.setState("levelSelect");
+          }
+        }
+
+        if (entity.hasComponent("momentum")) {
+          const momentum = unitize(entity.components.momentum);
+
+          let found;
+          const proposed = {x: entity.components.gridPosition.x + momentum.dx, y: entity.components.gridPosition.y + momentum.dy};
+          const entitiesToPush = [];
+          let wall = false;
+          do {
+            const proposedClampedInBounds = clamp(proposed, game.config.xDim-1, game.config.yDim-1);
+            if (!equivalence(proposed, proposedClampedInBounds)) {
+              break;
+            }
+
+            found = false;
+
+            const entitiesInCell = entitiesGrid[proposed.y][proposed.x];
+
+            for (let next of entitiesInCell.values()) {
+              if (next.hasComponent("alive")) {
+                if (next.hasComponent("stop")) {
+                  wall = next;
+                  found = false;
+                  break;
+                }
+                if (next.hasComponent("pushable")) {
+                  entitiesToPush.push(next);
+                  found = true;
+                }
+              }
+            }
+
+            proposed.x += momentum.dx;
+            proposed.y += momentum.dy;
+          } while(found);
+
+          if (wall) {
+            entity.removeComponent("momentum");
+          } else {
+            game.assets.move.play();
+            entitiesToPush.map((e) => {
+              const pushedParticleSpawner = game.createBorderParticles({maxSpeed: 0.1, minAmount: 10, maxAmount: 15});
+              pushedParticleSpawner.addComponent(game.components.Position(e.components.position));
+              pushedParticleSpawner.addComponent(game.components.Appearance({width: game.canvas.width / game.config.xDim, height: game.canvas.height / game.config.yDim}));
+              game.entities[pushedParticleSpawner.id] = pushedParticleSpawner;
+
+              e.addComponent(game.components.Momentum({...momentum}));
+            });
+          }
+        }
+      }
+    }
+    return thisChangedIds;
+  };
+  return { update };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/grid.js b/Homework/cs5410/bbiy/src/systems/grid.js
new file mode 100644
index 0000000..6d4cf84
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/grid.js
@@ -0,0 +1,71 @@
+game.system.Grid = (entitiesGrid) => {
+  let gridWidth = game.canvas.width / game.config.xDim;
+  let gridHeight = game.canvas.height / game.config.yDim;
+
+  const gameCoordsToGrid = ({ x, y }) => {
+    return { x: Math.floor((x+gridWidth/2) / game.canvas.width * game.config.yDim), y: Math.floor((y+gridHeight/2) / game.canvas.height * game.config.yDim) };
+  };
+
+  const gridCoordsToGame = ({ x, y }) => {
+    return { x: x * gridWidth, y: y * gridHeight };
+  };
+
+  const rebuildGrid = (entities) => {
+    let changedIds = new Set();
+    entities.map(entity => {
+      const { x, y } = entity.components.gridPosition;
+      if (!entitiesGrid[y][x].has(entity.id)) {
+        changedIds.add(entity.id);
+      }
+    });
+    entitiesGrid.forEach((row) => row.forEach((entitiesInCell) => {
+      for (let id of entitiesInCell.keys()) {
+        if (changedIds.has(id)) {
+          entitiesInCell.delete(id);
+        }
+      }
+    }));
+    changedIds.forEach(id => {
+      // TODO: Figure out why we HAVE to use game.entities rather than entities
+      // Hint: it breaks when changing a level in the menu
+      const entity = game.entities[id];
+      const { x, y } = entity.components.gridPosition;
+      entitiesGrid[y][x].set(entity.id, entity);
+    });
+  };
+
+  const update = (_elapsedTime, entities, changedIds) => {
+    gridEntities = Object.keys(entities).filter((x) => entities[x].hasComponent("gridPosition")).map((x) => entities[x]);
+    const thisChangedIds = new Set();
+    gridEntities.map((entity) => {
+      if (entity.hasComponent("appearance")) {
+        entity.components.appearance.width = gridWidth;
+        entity.components.appearance.height = gridHeight;
+      }
+      if (entity.hasComponent("gridPosition")) {
+        const oldGridCoords = entity.components.gridPosition;
+        if (entity.hasComponent("position")) {
+          const gameCoords = gridCoordsToGame(entity.components.gridPosition);
+          if (Math.abs(entity.components.position.x - gameCoords.x) >= gridWidth/2 || Math.abs(entity.components.position.y - gameCoords.y) >= gridHeight/2) {
+            entity.components.gridPosition = gameCoordsToGrid(entity.components.position);
+            if (entity.hasComponent("momentum")) {
+              entity.removeComponent("momentum");
+            }
+          }
+        }
+        if (!entity.hasComponent("position") || !equivalence(entity.components.gridPosition, oldGridCoords)) {
+          entity.components.position = {
+            ...entity.components.position,
+            ...gridCoordsToGame(entity.components.gridPosition)
+          };
+          thisChangedIds.add(entity.id);
+        }
+      }
+    });
+    rebuildGrid(gridEntities);
+    return thisChangedIds;
+  };
+
+
+  return { gameCoordsToGrid, gridCoordsToGame, update, gridWidth, gridHeight };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/keyboardInput.js b/Homework/cs5410/bbiy/src/systems/keyboardInput.js
new file mode 100644
index 0000000..1b399ca
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/keyboardInput.js
@@ -0,0 +1,46 @@
+game.system.KeyboardInput = () => {
+  "use strict";
+  const keys = {};
+  const keyPress = (event) => {
+    if (!event.repeat) {
+      keys[event.key] = true;
+    }
+  };
+  const removeKey = (event) => {
+    delete keys[event.key];
+  };
+  const update = (elapsedTime, entities, changedIds) => {
+    for (let id in entities) {
+      const entity = entities[id];
+      if (entity.hasComponent('controllable') && entity.hasComponent('alive')) {
+        const controls = entity.components.controllable.controls;
+        if (!changedIds.has(entity.id)) {
+          if (controls.includes('left') && keys[game.controls.left]) {
+            entity.addComponent(game.components.Momentum({ dx: -1, dy: 0 }));
+          } else if (controls.includes('right') && keys[game.controls.right]) {
+            entity.addComponent(game.components.Momentum({ dx: 1, dy: 0 }));
+          } else if (controls.includes('up') && keys[game.controls.up]) {
+            entity.addComponent(game.components.Momentum({ dx: 0, dy: -1 }));
+          } else if (controls.includes('down') && keys[game.controls.down]) {
+            entity.addComponent(game.components.Momentum({ dx: 0, dy: 1 }));
+          }
+        }
+      }
+    }
+    if (keys[game.controls.undo]) {
+      game.systems.undo.undo(entities);
+    }
+    if (keys[game.controls.reset]) {
+      game.loadLevelIndex(game.level);
+    }
+    if (keys["Escape"]) {
+      game.systems.menu.bringUpMenu();
+    }
+    Object.keys(keys).map((key) => delete keys[key]);
+
+    return new Set();
+  };
+  window.addEventListener("keydown", keyPress);
+  window.addEventListener("keyup", removeKey);
+  return { keys, update };
+}
diff --git a/Homework/cs5410/bbiy/src/systems/logic.js b/Homework/cs5410/bbiy/src/systems/logic.js
new file mode 100644
index 0000000..e8854c1
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/logic.js
@@ -0,0 +1,149 @@
+game.system.Logic = (entitiesGrid) => {
+  "use strict";
+  let currentVerbRules = [];
+  let previousVerbState = {
+    controllable: new Set(),
+    win: new Set(),
+  };
+  const isWord = (entity) => entity.hasComponent("gridPosition") && (entity.hasComponent("verb") || entity.hasComponent("noun"));
+  
+  const getFirstWordEntity = (gridPosition) => {
+    if (!equivalence(gridPosition, clamp(gridPosition, game.config.xDim, game.config.yDim))) {
+      return null;
+    }
+    for (let entity of entitiesGrid[gridPosition.y][gridPosition.x].values()) {
+      if (isWord(entity)) {
+        return entity;
+      }
+    }
+    return null;
+  };
+
+  const verbActionsToComponent = {
+    "stop": game.components.Stop(),
+    "push": game.components.Pushable(),
+    "you": game.components.Controllable({controls: ['left', 'right', 'up', 'down']}),
+    "burn": game.components.Burn(),    
+    "sink": game.components.Sink(),
+    "win": game.components.Win(),
+  };
+
+  const nounsToEntityCreators = {
+    "rock": game.createRock,
+    "wall": game.createWall,
+    "bigblue": game.createBigBlue,
+    "flag": game.createFlag,
+    "lava": game.createLava,
+    "water": game.createWater,
+  };
+  
+  const doOnRule = (rule, entities, direction) => {
+    const [applyee, application] = [entities[rule[0]], entities[rule[1]]];
+    const changedEntityIds = [];
+    if (applyee.hasComponent("noun")) {
+      const entityName = applyee.components.noun.select;
+      if (application.hasComponent("verb")) {
+        const verb = application.components.verb.action;
+        if (direction == "apply") {
+          currentVerbRules.push(rule);
+        }
+        for (let id in entities) {
+          const entity = entities[id];
+          if (entity.hasComponent("alive") && entity.hasComponent("name") && entity.components.name.selector == entityName) {
+            changedEntityIds.push(id);
+            const component = verbActionsToComponent[verb];
+            if (component) {
+              if (direction == "apply") {              
+                if (verb == "you") {
+                  if (!previousVerbState.controllable.has(id)) {
+                    const newYouParticleSpawner = game.createBorderParticles({colors: ["#ffc0cb", "#ffb6c1", "#ffc1cc", "#ffbcd9", "#ff1493"], minAmount: 80, maxAmount: 150, maxSpeed: 0.5});
+                    newYouParticleSpawner.addComponent(game.components.Position(entity.components.position));
+                    newYouParticleSpawner.addComponent(game.components.Appearance({width: game.canvas.width / game.config.xDim, height: game.canvas.height / game.config.yDim}));
+                    game.entities[newYouParticleSpawner.id] = newYouParticleSpawner;
+                  }
+                }
+                if (verb == "win") {
+                  if (!previousVerbState.win.has(id)) {
+                    game.assets.win.play();
+                  }
+                }
+                entity.addComponent(component);
+              } else if (direction == "deapply") {
+                if (entity.hasComponent("controllable")) {
+                  previousVerbState.controllable.add(id);
+                }
+                if (entity.hasComponent("win")) {
+                  previousVerbState.win.add(id);
+                }
+                entity.removeComponent(component.name);
+              }
+            }
+          }
+        }
+        if (direction == "apply") {
+          if (changedEntityIds.some((id) => previousVerbState.controllable.has(id))) {
+            previousVerbState.controllable = new Set();
+          }
+        }
+      }
+      if (application.hasComponent("noun")) {
+        const applicationEntityName = application.components.noun.select;
+        for (let id in entities) {
+          const entity = entities[id];
+          if (entity.hasComponent("name") && entity.components.name.selector == entityName) {
+            const e = nounsToEntityCreators[applicationEntityName]();
+            ["name", "sprite", "burnable", "sinkable"].map((name) => {
+              if (e.hasComponent(name)) {
+                entity.components[name] = e.components[name];
+              }
+            });
+          }
+        }
+      }
+    };
+    return changedEntityIds;
+  };
+  
+  const parseRules = (entities) => {
+    currentVerbRules.map((rule) => doOnRule(rule, entities, "deapply"));
+    currentVerbRules = [];
+    const isWordGridPositions = [];
+    const changedEntityIds = new Set();
+    entitiesGrid.forEach((row) => row.forEach((entitiesInCell) => {
+      for (let entity of entitiesInCell.values()) {
+        if (isWord(entity) && entity.hasComponent("verb") && entity.components.verb.action == "Is") {
+          isWordGridPositions.push(entity.components.gridPosition);
+        }
+      }
+    }));
+    let newRules = [];
+    isWordGridPositions.forEach((gridPosition) => {
+      const east = getFirstWordEntity({y: gridPosition.y, x: gridPosition.x - 1});
+      const west = getFirstWordEntity({y: gridPosition.y, x: gridPosition.x + 1});
+      const north = getFirstWordEntity({x: gridPosition.x, y: gridPosition.y - 1});
+      const south = getFirstWordEntity({x: gridPosition.x, y: gridPosition.y + 1});
+
+      if (east && west) {
+        newRules.push([east.id, west.id]);
+      }
+      if (north && south) {
+        newRules.push([north.id, south.id]);
+      }
+    });
+    newRules = newRules.sort((a, b) => (entities[b[1]].hasComponent("noun") ? 1 : -1) - (entities[a[1]].hasComponent("noun") ? 1 : -1));
+    newRules.map((rule) => doOnRule(rule, entities, "apply").map((id) => changedEntityIds.add(id)));
+    return changedEntityIds;
+  };
+  
+  const update = (_elapsedTime, entities, changedIds) => {
+    for (let id of changedIds) {
+      const changed = entities[id];
+      if (changed.hasComponent("verb") || changed.hasComponent("noun")) {
+        return parseRules(entities);
+      }
+    }
+    return new Set();
+  };
+
+  return { update, parseRules };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/menu.js b/Homework/cs5410/bbiy/src/systems/menu.js
new file mode 100644
index 0000000..abd6748
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/menu.js
@@ -0,0 +1,114 @@
+game.system.Menu = () => {
+  let state;
+
+  const menuElement = document.getElementById("menu"); 
+
+  const escapeEventListener = (e) => {
+    if (e.key == "Escape") {
+      setState('main');
+    }
+  };
+
+  const setState = (newState) => {
+    state = newState;
+    draw();
+  };
+
+  const bringUpMenu = () => {
+    game.running = false;
+    game.assets.music.pause();
+    window.addEventListener("keydown", escapeEventListener);
+    setState("main");
+  };
+
+  const hide = () => {
+    menuElement.style.display = "none";
+    game.startLoop();
+  };
+
+  const listenFor = (action, elementId) => {
+    const element = document.getElementById(elementId);
+    element.innerHTML = "Listening...";
+    const handleKey = (event) => {
+      window.removeEventListener("keydown", handleKey);
+      if (event.key == "Escape") {
+        element.innerHTML = menu.controls[action];
+        return;
+      }
+      game.controls[action] = event.key;
+      localStorage.setItem("controls", JSON.stringify(game.controls));
+      element.innerHTML = event.key;
+    };
+    window.addEventListener("keydown", handleKey);
+  };
+
+  const setLevel = (index) => {
+    game.loadLevelIndex(index);
+    hide();
+  };
+
+  const draw = () => {
+    menuElement.style.display = "block";
+    menuElement.innerHTML = `<h1><span style='color: blue'>Big Blue</span> Is <span style='color: green'>You</h1>`;
+    if (state == "main") {
+      menuElement.innerHTML += `
+        <div class='menu-button' onclick='game.systems.menu.setState("controls")'>Change Controls</div>
+        <div class='menu-button' onclick='game.systems.menu.setState("credits")'>Credits</div>
+        <div class='menu-button' onclick='game.systems.menu.setState("levelSelect")'>Select Level</div>
+      `;
+    }
+    else if (state == "controls") {
+      menuElement.innerHTML += `
+        <div>
+          <p>
+            Move left: <button id="moveLeft" onfocus='game.systems.menu.listenFor("left", "moveLeft")'>${game.controls.left}</button>
+            <br>
+            Move right: <button id="moveRight" onfocus='game.systems.menu.listenFor("right", "moveRight")'>${game.controls.right}</button>
+            <br>
+            Move up: <button id="moveUp" onfocus='game.systems.menu.listenFor("up", "moveUp")'>${game.controls.up}</button>
+            <br>
+            Move down: <button id="moveDown" onfocus='game.systems.menu.listenFor("down", "moveDown")'>${game.controls.down}</button>
+            <br>
+            Undo: <button id="undo" onfocus='game.systems.menu.listenFor("undo", "undo")'>${game.controls.undo}</button>
+            <br>
+            Reset: <button id="reset" onfocus='game.systems.menu.listenFor("reset", "reset")'>${game.controls.reset}</button>
+          </p>
+        </div>
+      `;
+    } else if (state == "credits") {
+      menuElement.innerHTML += `
+        <div>
+          <p>
+            Sprites from Baba Is You, as hosted <a href="https://www.spriters-resource.com/pc_computer/babaisyou/sheet/115231/">here</a>, and a few custom ones.
+            <br>
+            Background is from <a href="https://i.pinimg.com/originals/b2/2a/a2/b22aa22b2f3f55b6468361158d52e2e7.gif">PinImg</a>.
+            <br>
+            Music is <a href="https://www.youtube.com/watch?v=yQjAF3frudY">Fluffing A Duck</a> by Kevin MacLeod.
+            <br>
+            Other sound effects generated on <a href="https://www.sfxr.me/">SFXR</a>.
+            <br>
+            Developed by Logan Hunt, Ethan Payne
+          </p>
+        </div>
+      `;
+    } else if (state == "levelSelect") {
+      menuElement.innerHTML += `
+        <div>
+          <p> Select a level to play: </p>
+          ${
+            game.levels.map((level, index) => {
+              return `<div class='menu-button' onclick='game.systems.menu.setLevel(${index});'>${level.levelName}</div>`;
+            }).join("")
+          }
+      `;
+    }
+    if (!game.win) {
+      menuElement.innerHTML += "<div class='menu-button' onclick='game.systems.menu.hide()'>Resume Game</div>";
+    }
+    if (state !== "main") {
+      menuElement.innerHTML += "<div class='menu-button' onclick='game.systems.menu.setState(\"main\")'>Back</div>";
+    }
+  };
+    
+  return { bringUpMenu, setState, listenFor, hide, setLevel, state };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/particle.js b/Homework/cs5410/bbiy/src/systems/particle.js
new file mode 100644
index 0000000..56d8c47
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/particle.js
@@ -0,0 +1,57 @@
+game.system.Particle = () => {
+  "use strict"; 
+  const particleSpawners = {};
+  
+  const particleSpawner = ({colors, maxAmount, minAmount, minLife, maxLife, minRadius, maxRadius, maxSpeed, spawnFunction}) => {
+    return Array(randomInRange(minAmount, maxAmount)).fill(0).map(() => {
+      let particleSpec = {
+        x: Math.random(),
+        y: Math.random(),
+        dx: Math.random() * maxSpeed - maxSpeed / 2,
+        dy: Math.random() * maxSpeed - maxSpeed / 2,
+        radius: randomInRange(minRadius, maxRadius),
+        color: colors[randomInRange(0, colors.length-1)],
+        lifetime: randomInRange(minLife, maxLife),
+        elapsed: 0,
+      };
+      if (spawnFunction) {
+        particleSpec = {...particleSpec, ...spawnFunction(particleSpec)};
+      }
+      return particleSpec;
+    });
+  };
+
+  const update = (elapsedTime, entities, _changedIds) => {
+    for (let id in entities) {
+      const entity = entities[id];
+      if (entity.hasComponent("particles")) {
+        if (!particleSpawners[entity.id]) {
+          particleSpawners[entity.id] = particleSpawner(entity.components.particles.spec.spec);
+          entities[id].particleSprite = game.graphics.Sprite({
+            drawFunction: (elapsedTime, {x, y, width, height}, context) => {
+              let particleSpawner = particleSpawners[entity.id];
+              particleSpawner.map((particleSpec) => particleSpec.elapsed += elapsedTime);
+              particleSpawners[id] = particleSpawner.filter((particleSpec) => particleSpec.lifetime > particleSpec.elapsed);
+              particleSpawner = particleSpawners[id];
+              if (particleSpawner.length === 0) {
+                entities[id].removeComponent("alive");
+              }
+              particleSpawner.map((particleSpec) => {
+                const position = {x: (particleSpec.x * width) + x + particleSpec.dx * particleSpec.elapsed, y: (particleSpec.y * height) + y + particleSpec.dy * particleSpec.elapsed};
+                const fill = context.fillStyle;
+                context.fillStyle = particleSpec.color;
+                context.beginPath();
+                context.arc(position.x, position.y, particleSpec.radius, 0, 2 * Math.PI);
+                context.fill();
+                context.fillStyle = fill;
+              });
+            }
+          });
+        }
+      }
+    }
+    return new Set();
+  };
+
+  return { update };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/physics.js b/Homework/cs5410/bbiy/src/systems/physics.js
new file mode 100644
index 0000000..18c3cb3
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/physics.js
@@ -0,0 +1,16 @@
+game.system.Physics = () => {
+  const update = (elapsedTime, entities, changedIds) => {
+    for (let id in entities) {
+      const entity = entities[id];
+      if (entity.hasComponent("momentum") && entity.hasComponent("appearance")) {
+        const {dx, dy} = entity.components.momentum;
+        entity.components.position.x += dx * elapsedTime;
+        entity.components.position.y += dy * elapsedTime;
+        entity.components.position = clamp(entity.components.position, game.canvas.width - entity.components.appearance.width, game.canvas.height - entity.components.appearance.height);
+      }
+    }
+
+    return new Set();
+  };
+  return { update };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/render.js b/Homework/cs5410/bbiy/src/systems/render.js
new file mode 100644
index 0000000..e0db7e3
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/render.js
@@ -0,0 +1,26 @@
+game.system.Render = (graphics) => {
+  const update = (elapsedTime, entities, _changedIds) => {
+    graphics.clear();
+
+    const entitiesArray = Object.keys(entities).map(key => entities[key]);
+    const sortedEntities = entitiesArray.sort((a, b) => {
+      const aprior = a.hasComponent("loadPriority") ? a.components.loadPriority.priority : 0;
+      const bprior = b.hasComponent("loadPriority") ? b.components.loadPriority.priority : 0;
+      return bprior - aprior;
+    });
+
+    sortedEntities.forEach((entity) => {
+      if (entity.hasComponent("position") && entity.hasComponent("appearance") && entity.hasComponent("alive")) {
+        const drawSpec = {...entity.components.position, ...entity.components.appearance};
+        if (entity.hasComponent("sprite")) {
+          game.sprites[entity.components.sprite.spriteName].draw(elapsedTime, drawSpec);
+        } else if (entity.hasComponent("particles") && entity.particleSprite) {
+          entity.particleSprite.draw(elapsedTime, drawSpec); 
+        }
+      }
+    });
+
+    return new Set();
+  };
+  return { update };
+};
diff --git a/Homework/cs5410/bbiy/src/systems/system.js b/Homework/cs5410/bbiy/src/systems/system.js
new file mode 100644
index 0000000..f331401
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/system.js
@@ -0,0 +1 @@
+game.system = {};
\ No newline at end of file
diff --git a/Homework/cs5410/bbiy/src/systems/undo.js b/Homework/cs5410/bbiy/src/systems/undo.js
new file mode 100644
index 0000000..086d6b4
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/undo.js
@@ -0,0 +1,32 @@
+game.system.Undo = (entitiesGrid, logicSystem, gridSystem) => {
+  const states = [];
+
+  const update = (elapsedTime, entities, changedIds) => {
+    if (changedIds.size) {
+      const state = {};
+      for (let id in entities) {
+        if (entities[id].hasComponent("gridPosition")) {
+          state[id] = JSON.parse(JSON.stringify(entities[id].components));
+        }
+      }
+      states.push(state);
+    }
+    return new Set();
+  };
+
+  const undo = (entities) => {
+    let state = states.slice(0, -1).pop();
+    if (states.length > 1) {
+      states.pop();
+    }
+    for (let id in state) {
+      for (let componentName in state[id]) {
+        entities[id].addComponent({name: componentName, ...state[id][componentName]});
+      }
+    }
+    gridSystem.update(0, entities, new Set());
+    logicSystem.parseRules(entities);
+  };
+
+  return { update, undo };
+};