Scrap Ships v0.3

Enemy ships no longer kill you on contact

Enemy ships now shoot at you, getting hit loses scrap

Losing too much scrap causes your ship to temporarily downgrade until you regain the scrap

Enemy ships now have varying health and the heavy shot does double damage (1->2)

Nimble can now upgrade to Trident or Shogun

Tanker can now upgrade to Trident or Vanguard

Replaced explosion asset

Asteroids now drops 2-4 -> 1-3 scrap

Ship1 now drops 1-3 -> 2-4 scrap

Ship2 now drops 1-3 -> 3-5 scrap

Ship3 now drops 1-3 -> 4-6 scrap

Transitioning on the edge of the map should be a bit more intutitive