feat: magnetism

app/create-ecs.js

@@ -4,6 +4,7 @@ import Systems from '@/ecs-systems/index.js';
 export default function createEcs(Ecs) {
   const ecs = new Ecs({Components, Systems});
   const defaultSystems = [
+    'Attract',
     'ResetForces',
     'ApplyControlMovement',
     'IntegratePhysics',

app/create-player.js

@@ -40,6 +40,7 @@ export default async function createPlayer(id) {
       },
     },
     Health: {health: 100},
+    Magnet: {strength: 24},
     Position: {x: 128, y: 128},
     Speed: {speed: 100},
     Sound: {},

app/ecs-components/magnet.js

@@ -0,0 +1,7 @@
+import Component from '@/ecs/component.js';
+
+export default class Magnet extends Component {
+  static properties = {
+    strength: {type: 'uint8'},
+  };
+}

app/ecs-components/magnetic.js

@@ -0,0 +1,4 @@
+import Component from '@/ecs/component.js';
+
+export default class Magnetic extends Component {
+}

app/ecs-systems/apply-control-movement.js

@@ -14,6 +14,7 @@ export default class ApplyControlMovement extends System {
       default: ['Controlled', 'Forces', 'Speed'],
     };
   }
+
   tick() {
     for (const {Controlled, Forces, Speed} of this.select('default')) {
       if (!Controlled.locked) {

app/ecs-systems/attract.js

@@ -0,0 +1,39 @@
+import {System} from '@/ecs/index.js';
+import {normalizeVector} from '@/util/math.js';
+
+export default class Attract extends System {
+
+  static queries() {
+    return {
+      default: ['Magnet'],
+    };
+  }
+
+  tick() {
+    for (const entity of this.select('default')) {
+      const {Magnet, Position} = entity;
+      const aabb = {
+        x0: Position.x - Magnet.strength / 2,
+        x1: Position.x + (Magnet.strength / 2) - 1,
+        y0: Position.y - Magnet.strength / 2,
+        y1: Position.y + (Magnet.strength / 2) - 1,
+      };
+      for (const other of this.ecs.system('Colliders').within(aabb)) {
+        if (other === entity || !other.Magnetic) {
+          continue;
+        }
+        const difference = {
+          x: entity.Position.x - other.Position.x,
+          y: entity.Position.y - other.Position.y,
+        };
+        const toward = normalizeVector(difference);
+        other.Forces.applyImpulse({
+          x: Math.abs(toward.x) * 8 * Magnet.strength / difference.x,
+          y: Math.abs(toward.y) * 8 * Magnet.strength / difference.y,
+        });
+      }
+    }
+  }
+
+}
+

app/ecs-systems/colliders.js

@@ -90,6 +90,9 @@ export default class Colliders extends System {
       for (const otherId in wasCollidingWith) {
         if (!entity.Collider.collidingWith[otherId]) {
           const other = this.ecs.get(otherId);
+          if (!other || !other.Collider) {
+            continue;
+          }
           if (entity.Collider.collisionEndScriptInstance) {
             entity.Collider.collisionEndScriptInstance.context.other = other;
             Ticking.addTickingPromise(entity.Collider.collisionEndScriptInstance.tickingPromise());

app/ecs-systems/interactions.js

@@ -13,7 +13,6 @@ export default class Interactions extends System {
     for (const entity of this.select('default')) {
       const {Interacts} = entity;
       Interacts.willInteractWith = 0
-      // todo sort
       const entities = Array.from(this.ecs.system('Colliders').within(Interacts.aabb()))
         .filter((other) => other !== entity)
         .sort(({Position: l}, {Position: r}) => {