That's right, you would start with the centre node already activated, and as the game goes on, you would get skill points, that you can use to activate nodes that are adjacent to already activated nodes. Through a playthrough, you would get 20 skill points, plus the centre node already activated. This means you can't activate everything, so you'd have to think about which potential paths you might take. Ideally, you would get 7 big nodes by the end of the game, and all the little nodes connecting them.
The bigger ones give you a lot more bonuses than the little ones, but they're on the same theme. For example, a big node might give you +40% damage and +20% evasion against undead, the 4 little nodes around that big node might give you +20% initiative vs undead, or +10% accuracy and +10% damage again. It's kind of weird that you're getting damage and evasion. That's the nature of random generation, and so it might be worth the time to hand tailor the possible outcomes a bit more. But then the downside of that is that I have to put time into balancing them, as well.
Yeah, that's a big reason why I wanted to try a random skill map system. I think rogue likes do something like this, where every run, you can get a new combination of skills or items. I think that's why rogue likes have a lot of shelf life. However, there is a downside, I think. If I use a random skill map, I think there is a desire to finish a play-through quickly, so that a new skill map can be played. On a longer running game, I think players would instead want more control over what skill they can take. What do you think, does that sound right?
Instead, it might be a good idea to use the Skyrim model. The player would still only get 20 skill points or so, so they still can't do everything in one run. But, it still gives them a variety of alternative builds.
That's a great idea about the icons. I could put icons on the nodes, or maybe on the top left of each of the colored tiles, to indicate the them of each of the tiles.