""Mario Clash (マリオクラッシュ) is a game produced by Nintendo in 1995 for the Virtual Boy. It is the second "3D" Mario game, following the SNES game Super Mario Kart. It is heavily based on the original Mario Bros.
The objective of the game is to knock all the enemies in a particular level off ledges. This is accomplished by hitting them using Koopa shells, of which there are always two-if one shell is knocked into a pit, another appears to take its place. The majority of Mario's enemies need to be hit on the side (i.e. with a shell thrown from the background while the enemies are in the foreground or vice versa).
The player can choose to begin from any of the first forty stages.""
Source: Wikipedia, "Mario_Clash," available under the CC-BY-SA License.