super simple pong project for better understanding how to use signals to link together nodes in Godot

in the Goalzone script, a goal zone can emit 2 signals, score and start_countdown which are picked up by the main Arena scene which wraps everything. when Arena initializes it connects the score signal to the UI's _on_scored() function and the start_countdown signal to its own _on_countdown_timer_start() function.

signals in Godot will automatically call the connected functions when they emit a message, and can take a value. the signal score passes along the owner of the goal zone, which the UI sees and determines the correct player to credit with a goal. start_countdown just triggers the countdown timer in the Arena script to start the timer.