Secret Meta Techniques

[3rdProspect]

I've put just under 100 hours into CW2, and I feel like I'm intimately familiar with all the mechanics and almost all of the strategies in this game, but there are thousands of cool looking custom levels that seem impossible, only beatable with hacks or mods. Are there techniques and exploits you won't ever learn from the Story/Bonus missions that everyone has figured out? How are you intended to complete missions with conditions that make levels unwinnable by normal means, like when objects are placed on TOP of ground, making it undiggable/inaccessible?

[J]

If a building is attached to the ground you want to dig, first destroy the building (there's a button for that).
If the ground is blocked by a movable unit you can't or don't want to destroy, click & hold elsewhere to start digging, then move your mouse over the tiles you want to dig. Afterwards you can deselect the tiles you didn't want to dig. Do this while paused to avoid unwanted digging.