Big Freaking Dig is exactly what it says on the tin: get as many ores as possible, while fighting mobs and creating tools from new materials, such as cobalt - which can double the durability of a tool when adding a Mese Pickaxe Head onto a Cobalt Stick.
The refined tools allows users to make brand new tools which means Iron Tools can dig at Mese Level, and even further, or one could possibly triple durability of their tools. The choice is up to the user.
Another addition is the use of Oil, this useful material only generates underground in all layers. Oil can be used in the Oil TBM (based from TBM Reloaded), and can dig at double the speed, Oil may also be used to power furnaces, allowing people to remove their dependance from coal and use that for torches. Oil might also have more uses than people realize. It might also burn itself away if it generates next to lava.
https://github.com/Jordach/big_freaking_dig/archive/master.zip
Or, alternatively;
https://github.com/Jordach/big_freaking_dig/
No minetest_game derived mods will work within BFD, this is because I based BFD from my own code and not code from the original Minetest Game.
This game is more geared towards self-containment of it's own content - which means everything within BFD will work with BFD.
Why does the fist / tools take so long compared to minetest_game?
I did this to make the first day wooden tools only, and it makes it more of a challenge when mobs are surrounding you.
The second day should be stone tools, and the next week Steel, but until a few weeks (ingame), you should be able to make the first set of custom tools.
As soon as you reach Steel, the tool speed should match the old fist speed from Minetest, and the wooden tools (namely wooden pickaxe for stone)
Why does the mapgen look different?
This is because BFD uses the new map generators, which is known as MGV7 (or v7 in the world creator) and MGV5 (known as v5 respectively), which (depending on the mapgen) has rivers, real mountains, custom biome support, different styles of trees.