Way back when, mines used to be placed individually. Like you know how the minfield is drawn as a group of mines? Well, it used to be that mines were just one of those, and you placed them one by one. Each one of them detonating once before needing to be rebuilt.
It was only slightly less fiddley than you would imagine (the place 5 and 20 (or is it 10?) at a time bulk place feature really helped out). Because they were always just placed in clumps anyways, they were just grouped together graphically, able to deal multiple hits before going down (as semantically there are now multiple mines), got bigger hit boxes, and correspondingly reduced caps to the solution we have now.
