After having played Dan's version of Realtest for some time now, I must say that it is an intresting and entertaining version of Minetest (in this case, "game" may almost apply - although i'm very reluctant with that). Realtest is fine for anyone who wants a change from normal Minetest.
It starts with a nice caveman skin for the players. At first, all tools are terribly weak, and it takes time to figure out how everything works - which is part of the fun.
The trees are especially great. They come in several diffrent variants. Apart from nicely colored planks and logs as inventory images, the trees also drop sticks. With that automatic drop in combination with item pick, the wood is easier to obtain than moretrees wood. All wood types can be crafted into decorative chests (normal and locked), fences, nodebox-type ladders (also useful as handrails), doors, hatches, chairs, tables, bookshelves, slabs and stairs. I'd love to see this mod adapted for normal Minetest and used on servers more orientated towards building. Moretrees are beautiful as scenery and background, but in order to get wood, these Realtest trees would be far easier to handle.
Without metals, only stone may be gained as building material, and that's far more difficult than normal cobble (dig 9 stone, craft to macadam, put in fire to get one stone). For a long time, wood, sand and glass are the main materials. A metal chisel allows to get flat stone and desert stone, which can also be turned into stonebricks/desertstonebricks.
Metal processing is the core element of this game. You start with a stone anvil and a stone hammer and gradually upgrade through diffrent metal types and anvils until you eventually reach the strongest type of metal. Tools are crafted with the anvil and a special plan/receipe item (has to be crafted only once). Alloys can be created. Ores cannot be simply melted - you need to craft a clay mold first, put that into the fire in order to get a ceramic mold, which then can be used to melt the ore in it. Forging allows to get the future metal ingot out of the ceramic mold. It's even possible to do double metal ingots, sheets and double sheets. All of those diffrent metals produce tools and metal blocks. And there's a huge amount of metal types!
The decorations mod is also pretty nice. It provides shapes like vases, bowls, bowls with coal, small chests, chests, pyramids, etc. and can be found
here, except that the realtest version provides those shapes not only for malachite but also for like 10 other minerals with nice and diffrent textures.
Realtest is not the optimal game if you want to build. Obtaining building materials (apart from wood) does take a long time and is somewhat limited - which at least has the advantage that you won't see ugly cobble constructions everywhere - plus crafting with that 2x2 grid is just too limited. And then there was until recently fire - fire which can easily spread from a bonfire or furnace, even when the firemaker takes special care and does not have misciveous intentions. There is also no protection mod included and no home point.
All that makes the game very intresting and challenging for singleplayer or survival. Perhaps it can be extended with rich plant- and animal life in the future in order to stress the survival aspect.
The metal processing might be very intresting for players that also love technic. Perhaps some ideas could be integrated into technic (anvil, hammer, way of obtaining tools), while the result ought to be standard ingots created from standard ores.