Version 1.3, which includes all 34 levels planned for the final game, is out now! You can get it here: https://www.patreon.com/file?h=29486822&i=4354557.
It has 25 missions to complete, just like the original Rock Raiders, but as you clear levels, you will also unlock "bonus" levels playable in excavation and mission modes. Many of these bonus levels are "retro" levels paying a bit more direct homage to levels in the original game.
Because you can't actually unlock every level from a fresh save yet, I've included a little "cheat code": holding down Left Shift while starting a new game will give you a free 100% clear file with every level beaten and five fully-trained miners to start with.
My next priority is drawing up a new set of textures, to make the game a bit more readable.