games/flappybird is unresponsive to window size

[b7g]

Description

• [X] Bug Report
  1. the background does not resize with the window
  2. the upper/lower bounds seem to be fixed
  3. the spawn/despawn of the pipes is visible when the window is resized

Steps to reproduce the issue

1. start games/flappybird
2. maximize the window
3. let the bird drop to the bottom, fly the bird to the top [2]

Context

• OS: Ubuntu 22.04 LTS
• Software versions: Godot 3.4

[b7g]

fixed with #50