added music
duplicated particles for explosions
optimized generation of explosion visual effect
using Audio html elements to play music (no need for panning and effects, need for easy audio streaming/caching for music audio files)
changed grid dimensions to make it a perfect square
moved collision detection to think function of each object, only ship and asteroids do collision detection
replaced all forEach (and filter) calls with simple for statements to improve performance
inferior limit of 0 to bonus score to prevent negative scores
implemented alternation of collision checks (about 10 per second per object, asynchronous)
filter of collision checking by obj class
far spawn of asteroid when round change