Wow, you are still playing the game! That's a great pleasure to find out people return to it :) Yeah, screw the underground block, I removed it and even made it dark underground, so now the bunker is playable again :)
Hi, sorry to dissapoint you, but I had to reintroduce the underground blocking :D
The reason for this is that it did not play well with the new "Total Crush" effect when completly destroying a creation, and also with the new crushed blocks bar.
When underground blocks are pushed away by an explosion, they never hit something to be destroyed, so it's impossible to get a "Total Crush" with underground creations. Also a lot of players by mistake placed blocks undergroung, and it was impossible to achieve a "Total Crush" in those creations.