Every tile where work is performed (workshop, library, training dummy, etc) has a certain efficiency number attached to it, which affects how quickly the work is done by minions. The base efficiency is 100, and it is modified with the use of floors. The three types of floors that I've added so far (wooden, stone and carpet) add 2, 4 and 6 points of efficiency, respectively, to the nine tiles in the closest vicinity. Therefore, a tile's efficiency can grow to 154, if it has the best floor around and underneath. It is also dependent on the amount of light, and it can go down by 50% if you don't place torches in your dungeon. I'm also planning other floor types that have magical effects on whomever is standing on them, and they will be used as part of dungeon defenses. They are yet to be designed, though. Another feature that I planned were room upgrades, and I started with adding new types of training dummies. I also used the occasion to modify the experience leveling algorithm. The three types of dummy (wooden, iron, and steel) allow gaining respectively 3, 7, and 12 experience levels. The number is the same for every creature, so both an orc and a legendary humanoid can gain 7 levels on iron dummies. The training speed is now constant, and it takes 300-400 turns to gain a level (the number will be subject to balancing :)). I'm also going to tone down leveling during combat, as it's hugely overpowered now. I need to figure out some clever algorithm to make it still relevant, though.
The last feature that will go into Alpha20, probably, is a new material: steel. As you know, steel is produced from iron and other elements by the means of metallurgy, and it will be the same in KeeperRL. After researching appropriate technology, and getting enough materials, you will build furnaces that produce steel plates. The amount of resources and time that you'll have to sacrifice to produce a meaningful amount will be large, therefore this will be a late-game advancement. You'll use the steel plates to create weapons, armor, training dummies, and other nice things. Cool stuff! I'll also test whether it makes sense to add an analogous method of iron production, such that you'll melt iron ore in furnaces to create iron plates, which will be used for buildings and crafting. It would be a nice way to add even more progression to the game, although I'm not sure if it will work nicely with other systems. Any input will be greatly appreciated. For now, that's all folks. :)