I have to show you small mod which adds to minecraft simple physics like in a sand or gravel to other block like stone, stone brick, sandstone etc. Now with this mod you CAN’T place stone (or others) blocks in air. You must have some platform under it. Now you can’t build buildings from up to down but you must build from down to up. Other feature is you can be buried in cave by dirt. – It’s cool feature of this mod. You can see all of the features on the video:
Mod is fully compatible with Minecraft 1.2.5
If you want to have latest update look here.
Minecraft Map Database 