When I was 13, me and a friend (G.) wrote tons of levels for the Commodore 64 version of the 'Boulderdash Construction Kit'.
Previously thought missing, I found the 42 levels ('caves') on some disks in my mother's attic 2 months ago. I got another 12 later on (in set 4).
I got them off the disks with a 1541 drive and a special cable connected to my PC parallel port, and after some attempts, I managed to rescue all known caves.
I've loaded them into WinVice via the monitor so that there's 16 levels per snapshot. Load up any of the 4 snapshots and select a level by moving the joystick up.
Be warned, some caves are extremely obscure and will take some time to figure out. However, great use is made of the features of the game in these caves, and they are much more innovative than the levels included with the editor.
All levels (c) 1992 Jeremy Smith and G. Booth
Boulderdash IV Runtime distributed under fair use
Cave levels are saved as '.cav' files on your C64 or '.int'. cav is a cave, int is an intermission.
Each level is 498 bytes on disk.
The first 2 bytes are info, followed by map data.
The game/runtime (not the construction kit program) can have up to 16 caves in memory.
The caves load at 7000h and are separated by 200h, and 8E00h to 9000h is the last slot, level 16.
Any cave with all 0's (as in 003 above) and Boulderdash displays the first cave in memory.