I managed to get the icy alien part of the island to look really good. There's snow and ice everywhere. I've placed a petrol station with vehicles and pumps, etc. All of that has been frozen over and looks really good.
I've started placing alien enemies into the map. There are various types that have different behaviour. The small aliens shoot ice shards and jump at the player to attack them. Larger ones fly in the air and shoot large ice shards. The largest alien war machine i a four-legged walker that shoots a large energy ball. It also has a freeze beam that freezes the player in ice. If the player gets too close the walker it can grab them with a tentacle and throw them through the air.
I've got a problem with vegetation and roads but I'll leave that until my next post.