So I felt like sharing with you guys a very small alteration to Mari0; something which existed in the original SMB1 but never exploited until the upteen million ROM hacks that sprouted over the years. And quite supringsly with me, this is a feature I would prefer not to be incorporated into core Mari0, for that it would destroy/break certain levels with accessible Shells and create a large amount of cutoff, especially for ones that know how to "dig" using the Portal Gun and a lone Shell.
So what does this mod do? It changes the properties for the default "Ground" blocks, allowing them to be destroyed with hits form below or a Shell. To accomplish this, I only made a small edit to the smbtiles.png file. Nothing else was altered.
The travesty magic at work: