During these last few days, I have been redesigning the entry and exit system of the asteroid field. I didn't really like the portal system, so I rejected it. I'm sure I can reuse it for other things, but I'll stick with the previous entry system using a mothership from which you take off and land. 
The ship takes you to the surroundings of the asteroid field and disappears. When the player has finished his mission, he calls the mothership that appears randomly outside the field. To locate it we have enabled a radar that tells us in which direction to locate our mother ship.
I think it is a more dynamic system and much more fun. 

During these last days we are working on the access and exit portals to the asteroid fields.
My intention is to complete the main cycle of the game mechanics. That is, enter the asteroid field, gather the necessary crystals and flee, leaving through the portal without being destroyed.
With this we would have the basic mechanics. Then, step by step, we would add the rest of what we have in mind.
(More enemies, final bosses, experience gain, weapon shop and ship upgrades, and power ups)