Story from the instruction booklet
Each level consists of two layers, a foreground and a background, that are connected by Warp Pipes. When Mario enters the stage through the rope, he can decide which layer to start in. Each layer may have two floors or floating platforms between the two floors. Later levels will have slippery frozen platforms.
To beat each level, Mario must knock targeted enemies off the stage before the Time Limit. Stomping on Koopas will provide Mario with his only weapon, their Turtle Shells. There are always two Koopas; if one gets knocked off, another one takes its place. Enemies and thrown shells can travel through the pipes. Many enemies need to be hit from the side to stun them, thus Mario must throw shells from the background to the foreground and vice-versa in order to hit them but the shell will be lost if he misses. It is also possible to ricochet off of multiple enemies this way. Stunned targets can be dispatched by kicking them or throwing a shell at them again. However, all stunned enemies can recover, including the Koopa he is holding. Also, the last target of each level will move faster. Stunning a target is worth 100 points while dispatching one is worth 500. Defeating multiple enemies with a single throw will give bonus points.
The game allows the player to select any of the first 40 levels to start. After clearing all 99 levels, the game loops back to Level 1 but all the enemies move faster. There is no true ending but reaching the maximum number of points (999,999) will award the player with a cutscene. Between some levels is the Bonus Chance where Mario can collect coins for extra points or get an extra life. The other method of getting extra lives is to accrue enough points. When this is achieved, a 1UP sign will fly across the screen. If Mario hits it with a shell, he will get a second extra life. This sign won't show up if the threshold is crossed during Bonus Chance. It is also impossible to hit if it appears after Mario defeats the last target. There is no save function and high scores are not recorded.
Cameos from other Super Mario series characters appear in a Nintendo border after every 100,000 points scored. In the Bonus Chance, Luigi, Princess Toadstool, Yoshi, and Toads appear in the bleachers.
Pre-release and unused content
Mario Clash was originally a mini-game which was seen in VB Mario Land, an unreleased Virtual Boy game which was shown at the Winter Consumer Electronics Show in Las Vegas, 1995. The game Mario Bros. VB itself was a earlier version of Mario Clash. It was shown as a demo game at the Shoshinkai expo in Japan, which took place on November 15th and 16th, 1994.
The Electronic Entertainment Expo in May 1995 revealed that the Mario Bros. minigame (which was previously known to be included in the VB Mario Land demo), was now being developed as a stand-alone game titled Mario Clash, which was planned to be released as a launch title for the Virtual Boy. For unknown reasons, there were no further reports of VB Mario Land being developed.
The game received mixed reviews. ScrewAttack named this video game "The second worst Mario video game of all time", while other reviews were more positive. The Video Game Critic gave it an A and called it a "must have for Virtual Boy owners".
References in later games
Names in other languages