I hope this is the appropriate forum to post this request for information. If not, I apologize. I posted this to sci.astro last night but, after looking at some of the posts there, I came to the conclusion that newsgroup is maybe not the best place to find astronomy-related discussions. So I came over here since I remembered it from a long-ago recommendation.

I have been an astronomy buff most of my life and have been working on a Java-based "space empire" game for the past year. I'm not here to plug the game or anything, and it's going to be a freebie, anyway.

However, I am taking pains to ensure that the star & planet models are as realistic as possible without taking the fun out of the game. In other words, I want the planet/star models to have variety without being overly complex. Here's what I have so far...

STARS
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The stellar types currently in the game:
Brown Dwarf (functions as a star for game purposes)
Red
Orange
Yellow
White
Blue
Blue Giant
Red Giant
Red Supergiant
Orange Giant
Yellow Hypergiant
White Dwarf
Neutron
Black Hole

In the game, it is possible for a Supernova-type event to occur for most types of stars. For main sequence stars, this would essentially result in a transition to their giant stage while, for giant stars, it would be the transition to the White Dwarf, Neutron or Black Hole types.

What I would like expert help with, in particular, is information on any missing stellar types and a rundown on what mass levels trigger which transition. For example, what determines when stars go to the Blue-Red-Orange-Yellow giant types?

Multiple star systems are going to be added a later time.

PLANETS
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The various Planet types are more complex because there are more variables involved. I am currently using 4 variables for planets that are candidates for colonization by players with the appropriate technology:

1) Mass - from Mars (lower end) to larger-than-Earth (upper end)
2) Stellar Zone - hot, warm, temperate, cool and cold. Liquid water only possible in the middle 3 zones.
3) Atmosphere - none, greenhouse (CO2), terran (N&O2) and Titanesque (N&methane)
4) Water levels - none, damp, wet, flooded

Based on those 4 variables, I generate a wide range of planet types. A graphic mockup should make this easier to visualize (at the end of this post)...

Anyway, I am particularly interested in any input as to other important planet variables that are missing or perhaps other types of possible atmospheres for planets. Keep in mind that gas giants are not in the game (yet) because they are not considered suitable candidates for colonization. I do have "volcanic" and "molten" planets in the game, but they are also not colonizable.

I really want to provide as much realism as possible within the game without overwhelming the players in details. Thanks in advance for any constructive comments or criticism you can provide.

Here is the graphic mockup of the planet types. Let me know if I should change this to a link instead... (Please overlook the graphics for the planets. The Toxic planet, for example, has been switched to a more appropirate shot of Titan while shot of Io is now used for the Volcanic planet).