Fix ladder entry/exit logic to handle top entry and prevent premature exits

src/entities/Player.js

@@ -14,6 +14,7 @@ export default class Player {
         this.lives = 3;
         this.onLadder = false;
         this.atLadderTop = false;
+        this._enteredFromTop = false;
 
         // Create physics sprite
         this._sprite = scene.physics.add.sprite(x, y, 'player', 0);
@@ -51,11 +52,13 @@ export default class Player {
     _handleLadder() {
         const sprite = this._sprite;
         const cursors = this._cursors;
+        const body = sprite.body;
 
         // Tile at player center (for body-of-ladder detection)
         const centerTile = this._laddersLayer.getTileAtWorldXY(sprite.x, sprite.y);
-        // Tile at player feet (for ladder-top detection)
-        const feetTile = this._laddersLayer.getTileAtWorldXY(sprite.x, sprite.y + 116);
+        // Tile just below body bottom (body bottom = sprite.y + 120; +2 puts us inside
+        // the tile when standing on it, since physics places body bottom at tile top)
+        const feetTile = this._laddersLayer.getTileAtWorldXY(sprite.x, sprite.y + 122);
 
         const centerIsLadder = centerTile && TilePropertyHelper.isLadder(centerTile.index);
         const feetIsLadderTop = feetTile && TilePropertyHelper.isLadderTop(feetTile.index);
@@ -79,8 +82,16 @@ export default class Player {
                 return;
             }
 
-            // Exit ladder if center is no longer over a ladder tile
-            if (!centerIsLadder) {
+            // Once the center reaches a ladder tile we are fully on the ladder
+            if (centerIsLadder) {
+                this._enteredFromTop = false;
+            }
+
+            // Exit if center is no longer over a ladder tile.
+            // Exception: when we entered from the top the center starts above the ladder;
+            // suppress the exit until the player descends into the rungs, or until
+            // they press up (changing their mind).
+            if (!centerIsLadder && (!this._enteredFromTop || cursors.up.isDown)) {
                 this._exitLadder();
             }
         } else {
@@ -92,12 +103,21 @@ export default class Player {
                 sprite.body.setVelocityX(0);
                 // Snap horizontally to ladder center
                 sprite.x = centerTile.pixelX + 64;
+            // Enter from the top: standing on the top rung tile, pressing down
+            } else if (feetIsLadderTop && cursors.down.isDown && body.blocked.down) {
+                this._enteredFromTop = true;
+                this.onLadder = true;
+                sprite.body.setGravityY(-800);
+                sprite.body.setVelocityY(200);
+                sprite.body.setVelocityX(0);
+                sprite.x = feetTile.pixelX + 64;
             }
         }
     }
 
     _exitLadder() {
         this.onLadder = false;
+        this._enteredFromTop = false;
         this._sprite.body.setGravityY(0); // Remove local gravity override; world gravity resumes
     }