feat: implement room fallout behavior with invincibility bottom bounce mechanic

Author: CoolSpring8

src/GameScene.ts

@@ -261,7 +261,7 @@ export class GameScene extends Phaser.Scene {
 
     if (this.pauseMenu.isOpen) {
       this.updatePauseInput();
-      const snapshot = this.player.getSnapshot();
+      let snapshot = this.player.getSnapshot();
       this.playerView.render(snapshot);
       this.renderLighting(snapshot);
       this.updateHUD(snapshot, []);
@@ -295,7 +295,7 @@ export class GameScene extends Phaser.Scene {
 
     if (this.roomTransition) {
       this.updateRoomTransition(rawFrameDt);
-      const snapshot = this.player.getSnapshot();
+      let snapshot = this.player.getSnapshot();
       this.playerView.render(snapshot);
       this.renderLighting(snapshot);
       this.updateHUD(snapshot, effects);
@@ -380,13 +380,17 @@ export class GameScene extends Phaser.Scene {
         }
       }
 
-      const snapshot = this.player.getSnapshot();
+      let snapshot = this.player.getSnapshot();
       this.playerView.tick(snapshot, stepEffects, this.fixedDt);
       effects.push(...stepEffects);
 
       if (this.tryStartRoomTransition(snapshot)) {
         break;
       }
+      if (this.tryHandleBottomFallout(snapshot)) {
+        break;
+      }
+      snapshot = this.player.getSnapshot();
 
       this.updateCamera(snapshot, this.fixedDt);
       this.accumulator = subFloat(this.accumulator, this.fixedDt);
@@ -871,6 +875,47 @@ export class GameScene extends Phaser.Scene {
     return true;
   }
 
+  private tryHandleBottomFallout(snapshot: ReturnType<Player["getSnapshot"]>): boolean {
+    const bounds = this.currentRoom.bounds;
+    if (snapshot.top <= bounds.y + bounds.h) {
+      return false;
+    }
+
+    const roomBelow = findAdjacentRoom(this.rooms, this.currentRoom, "down", snapshot.centerX);
+    if (roomBelow !== null) {
+      return false;
+    }
+
+    if (this.beginBottomFalloutRespawn(snapshot)) {
+      return true;
+    }
+
+    this.player.bounceFromBottom(bounds.y + bounds.h, this.keys.jump.isDown);
+    return false;
+  }
+
+  private beginBottomFalloutRespawn(snapshot: ReturnType<Player["getSnapshot"]>): boolean {
+    if (!this.player.die({ x: 0, y: 0 })) {
+      return false;
+    }
+    this.requestDeathShake();
+    this.controls.clearTransientState();
+    this.accumulator = 0;
+    this.freezeTimer = 0;
+    this.roomTransition = null;
+    this.startDeathRespawnSequence({
+      kind: "normal",
+      exploded: false,
+      revealStarted: false,
+      respawnStarted: false,
+      respawnSourceX: snapshot.centerX,
+      respawnSourceY: snapshot.centerY,
+      knockback: null,
+    });
+    this.startTransitionExplosion(snapshot);
+    return true;
+  }
+
   private enforceCurrentRoomTopLimit(): void {
     const snapshot = this.player.getSnapshot();
     const roomAbove = findAdjacentRoom(this.rooms, this.currentRoom, "up", snapshot.centerX);

src/player/Player.ts

@@ -38,6 +38,7 @@ const USED_HAIR_LERP_RATE = 6;
 const BOUNCE_AUTO_JUMP_TIME = 0.1;
 const BOUNCE_VAR_JUMP_TIME = 0.2;
 const BOUNCE_SPEED = -140;
+const BOTTOM_BOUNCE_JUMP_HELD_SPEED = -180;
 const SWEAT_JUMP_HOLD_TIME = 0.12;
 const ZERO_DIRECTION = { x: 0, y: 0 };
 const EMPTY_INPUT: InputState = {
@@ -636,6 +637,21 @@ export class Player extends Actor {
     this.emit({ type: "bounce", dirY: -1 });
   }
 
+  bounceFromBottom(bottomLimit: number, jumpHeld: boolean): void {
+    const hitbox = this.requireBodyHitbox();
+    if (this.getHitboxBottom() > bottomLimit) {
+      this.y = this.entityYForFoot(hitbox, bottomLimit);
+    }
+
+    this.bounce();
+    if (jumpHeld) {
+      this.varJumpTimer = BOUNCE_VAR_JUMP_TIME;
+      this.autoJump = true;
+      this.autoJumpTimer = BOUNCE_AUTO_JUMP_TIME;
+      this.varJumpSpeed = this.vy = BOTTOM_BOUNCE_JUMP_HELD_SPEED;
+    }
+  }
+
   enforceTopLimit(minTop: number): void {
     const bounds = this.getHitboxBounds();
     if (bounds.y >= minTop) {

tests/gameplay/transition-behavior.test.ts

@@ -71,4 +71,18 @@ describe("Transition behavior", () => {
     const result = stepOnce(player, makeInput());
     expect(result.snapshot.vy).toBe(-140);
   });
+
+  test("bottom bounce clamps to the room edge and jumps higher while jump is held", () => {
+    const world = buildWorld([]);
+    const player = createPlayer(world, 100, 100);
+
+    player.bounceFromBottom(92, true);
+
+    const bounced = player.getSnapshot();
+    expect(bounced.bottom).toBe(92);
+    expect(bounced.vy).toBe(-180);
+
+    const result = stepOnce(player, makeInput({ jump: true }));
+    expect(result.snapshot.vy).toBe(-180);
+  });
 });