The game is so well designed. Look for example at the stat upgrade system. You find scrolls, and it offers you to upgrade one of three stats for that run, brutality/tactics/survival (not that the name matters, other games it could have been str/dex/sta). One of three choices, simple.
But they affect so much:
-They affect what weapons and items you are going to use in the whole run, because each is color coded, associated to one or two of the three stats, and their damage scale up with the stat. So if you go with brutality (red), you are going to want to be focused more on red weapons. This has interesting ramifications because the ‘optimal’ thing would be to have all four slots with red weapons, but sometimes a good red weapon can be a very good complementary synergy with a purple item that you find at random on a shop, so maybe you then would want to be less ‘optimal’, as the synergy overcomes the lower damage?
-You also gain health with each stat. But you don’t win the same amount with each no, no. Red is normal weapons, and it gives you a normal health amount. Purple is deployables and traps, which is overall a safer, easier way to play, and in exchange it gives less health. Green only has associated with shields, some misc items and very few weapons, it isn’t as useful, so in exchange it gives more health than the other two. That’s already an interesting balance.
But there is more. The higher you have a stat, the less health you gain with each new point. So that’s another balanced point, you can choose to be overall tanky with a stat configuration like 9/7/7, or you can go glass cannon and if you are using red weapons, choosing something 14/4/5. That gives you more damage with your red weapons, but your health pool will be smaller. Of course if you have a varied set of weapons of different colors, you won’t need to have a smaller health pool, but then you won’t be maximizing your damage.
-Finally most (but not all) mutations (you pick 3 over the course of the run) are also color coded, and scale up their utility with the appropriate stat. So again, you are going to want get red mutations if are focusing on the red stat, but it isn’t always that easy. Sometimes you may be using green items (like spear + shield) and it would be nice some melee-focused red mutations, or maybe you are doing a glass cannon build with purple traps and bows and would like a grey (uncolored) mutation that doubles ammo.