bug fixes + functionality update

Added Combos:

You can start a combo by bouncing ball(s) off your paddle multiple times without dropping one. The better your combo is, the more powerful your balls become!

This also makes it so that not every game is "mash-fire-button-until-I-win." Think of it as a strategic balance update.

Also, the "paddle speed up" block (purple) has been changed to the "defense up" block. I've made a completely different way to calculate damage that hopefully makes the game more challenging, exciting, and possibly frustrating!

Bugfixes:

- High scores actually update now

- Scores are added and calculated as intended

- The menu no longer breaks every time

- Computer balls no longer randomly disappear because trail renderers are quirky

- Lights are brighter so you see almost nothing when it goes dark, not literally nothing

Known Issues:

- The menu breaks when you click repeatedly on a button really really quickly. 

- Sometimes the computer paddle runs away while the countdown timer is going, but it always comes back. This doesn't actually impact the functionality of the game, but is kinda annoying.

- The shooting line from the player doesn't always scale correctly.

- Balls appear to bounce *through* solid blocks every once in a while.

Upcoming Features:

- Achievements!

- More sound effects!

- Different types of "ammo!"

- Make the shooting line more pretty

- Make the UI less ugly

- Pause menu for those emergency  mid-shootout bathroom breaks