Endgame tweaks

[Cogito]

Make the game more winnable.

By focusing on increasing an enemy's spawn radius relative to the player's current radius, the total size of enemies increases as the square of the player's area.

When enemies total area increases linearly with the player's area the game is much more winnable. This requires increasing enemy's spawn radius relative to the square root of the player's current radius, and a tweaking of the constant factor in this relationship to ensure the enemies remain competitive.

[franzenzenhofer]

hi thx. the game is now definitely more winable, without becoming too easy