*The two lowest slopes of your tile will form the bottom tile border of your opening, which will be completely flat. The top of your mine opening will be completely flat as well.
*'''You cannot [[Mining#Surface_mining|surface mine]] to correct an oddly shaped entrance once it is open.''' So you must make sure to have the tile in the exact shape you want it to be before you open the mine.
*If you don't want any ugly water on the floor in the mine, ensure that both lower corners of the entrance are at least at height 26 28 (hover the corner with the mouse).
*The maximum height of a tunnel entrance is 270 slope, but you would not be able to continue mining because of ceiling height restrictions. Tunnel slopes should be less than 235.
*The maximum height of an tunnel entrance is 90 slope if you plan to add a mine door.