From 3844363b150c0b36cb8505229b6d695724e473d0 Mon Sep 17 00:00:00 2001
From: Marc Flerackers <marc.flerackers@ponos.co.jp>
Date: Mon, 27 May 2024 19:00:44 +0900
Subject: [PATCH] Added gravity vector, modified all logic to support up/down
 correctly with any direction

---
 CHANGELOG.md                   |  1 +
 src/components/physics/body.ts | 43 ++++++++++++++++++++++------------
 src/kaboom.ts                  | 24 +++++++++++++------
 src/types.ts                   |  8 +++++++
 4 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f2071c6..4ea4206c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - added support for texture larger than 2048x2048
 - added `chooseMultiple()` and `shuffle()` helper functions
 - added `getSceneName()` to get the current scene name
+- added support for gravity direction
 
 ### v3000.1.17
 
diff --git a/src/components/physics/body.ts b/src/components/physics/body.ts
index ef45130e..511aaec9 100644
--- a/src/components/physics/body.ts
+++ b/src/components/physics/body.ts
@@ -91,7 +91,9 @@ export function body(opt: BodyCompOpt = {}): BodyComp {
                 this.onPhysicsResolve((col) => {
                     if (internal.game.gravity) {
                         if (col.isBottom() && this.isFalling()) {
-                            this.vel.y = 0;
+                            this.vel = this.vel.reject(
+                                internal.game.gravity.unit(),
+                            );
                             curPlatform = col.target as GameObj<
                                 PosComp | BodyComp | AreaComp
                             >;
@@ -102,7 +104,9 @@ export function body(opt: BodyCompOpt = {}): BodyComp {
                                 this.trigger("ground", curPlatform);
                             }
                         } else if (col.isTop() && this.isJumping()) {
-                            this.vel.y = 0;
+                            this.vel = this.vel.reject(
+                                internal.game.gravity.unit(),
+                            );
                             this.trigger("headbutt", col.target);
                         }
                     }
@@ -119,7 +123,7 @@ export function body(opt: BodyCompOpt = {}): BodyComp {
                     willFall = false;
                 }
 
-                let updateY = true;
+                let addGravity = true;
 
                 if (curPlatform) {
                     if (
@@ -139,21 +143,28 @@ export function body(opt: BodyCompOpt = {}): BodyComp {
                             );
                         }
                         lastPlatformPos = curPlatform.pos;
-                        updateY = false;
+                        addGravity = false;
                     }
                 }
 
-                if (updateY) {
-                    const prevVelY = this.vel.y;
+                if (addGravity) {
+                    const prevVel = this.vel.clone();
 
-                    this.vel.y += internal.game.gravity * this.gravityScale
-                        * k.dt();
-                    this.vel.y = Math.min(
-                        this.vel.y,
-                        opt.maxVelocity ?? MAX_VEL,
+                    // Apply gravity
+                    this.vel = this.vel.add(
+                        internal.game.gravity.scale(this.gravityScale * k.dt()),
                     );
 
-                    if (prevVelY < 0 && this.vel.y >= 0) {
+                    // Clamp velocity
+                    const maxVel = opt.maxVelocity ?? MAX_VEL;
+                    if (this.vel.slen() > maxVel * maxVel) {
+                        this.vel = this.vel.unit().scale(maxVel);
+                    }
+
+                    if (
+                        prevVel.dot(internal.game.gravity) < 0
+                        && this.vel.dot(internal.game.gravity) >= 0
+                    ) {
                         this.trigger("fall");
                     }
                 }
@@ -182,17 +193,19 @@ export function body(opt: BodyCompOpt = {}): BodyComp {
         },
 
         isFalling(): boolean {
-            return this.vel.y > 0;
+            return this.vel.dot(internal.game.gravity) > 0;
         },
 
         isJumping(): boolean {
-            return this.vel.y < 0;
+            return this.vel.dot(internal.game.gravity) < 0;
         },
 
         jump(force: number) {
             curPlatform = null;
             lastPlatformPos = null;
-            this.vel.y = -force || -this.jumpForce;
+            this.vel = internal.game.gravity.unit().scale(
+                -force || -this.jumpForce,
+            );
         },
 
         onGround(this: GameObj, action: () => void): EventController {
diff --git a/src/kaboom.ts b/src/kaboom.ts
index a11e46a9..b2267bf4 100644
--- a/src/kaboom.ts
+++ b/src/kaboom.ts
@@ -705,7 +705,7 @@ export default (gopt: KaboomOpt = {}): KaboomCtx => {
         root: make([]),
 
         // misc
-        gravity: 0,
+        gravity: vec2(0, 1),
         scenes: {},
         currentScene: null,
 
@@ -3370,11 +3370,19 @@ export default (gopt: KaboomOpt = {}): KaboomCtx => {
     }
 
     function setGravity(g: number) {
-        game.gravity = g;
+        game.gravity = game.gravity.unit().scale(g);
     }
 
     function getGravity() {
-        return game.gravity;
+        return game.gravity.len();
+    }
+
+    function setGravityDirection(d: Vec2) {
+        game.gravity = d.unit().scale(game.gravity.len());
+    }
+
+    function getGravityDirection() {
+        return game.gravity.unit();
     }
 
     function setBackground(...args) {
@@ -4249,16 +4257,16 @@ export default (gopt: KaboomOpt = {}): KaboomCtx => {
             return !this.displacement.isZero();
         }
         isLeft() {
-            return this.displacement.x > 0;
+            return this.displacement.cross(game.gravity) > 0;
         }
         isRight() {
-            return this.displacement.x < 0;
+            return this.displacement.cross(game.gravity) < 0;
         }
         isTop() {
-            return this.displacement.y > 0;
+            return this.displacement.dot(game.gravity) > 0;
         }
         isBottom() {
-            return this.displacement.y < 0;
+            return this.displacement.dot(game.gravity) < 0;
         }
         preventResolution() {
             this.resolved = true;
@@ -4983,6 +4991,8 @@ export default (gopt: KaboomOpt = {}): KaboomCtx => {
         toWorld,
         setGravity,
         getGravity,
+        setGravityDirection,
+        getGravityDirection,
         setBackground,
         getBackground,
         getGamepads: app.getGamepads,
diff --git a/src/types.ts b/src/types.ts
index 9fd99ad6..9dacdc54 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1903,6 +1903,14 @@ export interface KaboomCtx {
      * @group Info
      */
     getGravity(): number;
+    /**
+     * Set gravity direction.
+     */
+    setGravityDirection(d: Vec2): void;
+    /**
+     * Get gravity direction.
+     */
+    getGravityDirection(): Vec2;
     /**
      * Set background color.
      *