Devlog 30.07.20

Changes:

• Added a game over message, which also shows you your score and maximum score multiplier.
• Changed movement again, so now the acceleration is constant, instead of depending on current direction and speed.
• Added circles around powerups indicating how long time they have left until they expire.
• Changed asteroid, ufo spawn amounts and speed.
• Added new sounds to heavy ufos.
• Added particles to ufos.
• Updated description.