Blaster Master is an NES action game released by Sunsoft in 1988. It features both side-scrolling and overhead shooting stages. It is renowned for its music, questionable plotline, and high level of difficulty. In Japan it was released as Chou Wakusei Senki MetaFight without the benefit of having anything to do with the rescue of a frog.
Everything is pretty normal for Jason Frudnick. He's a teenage boy; he does things that kids do. He's probably been in a bit of trouble with his parents, but he can talk to Fred--his pet frog--when he's feeling down. Things are pretty normal for Jason. That is, until one fateful day.
One day his pet frog decides to go hopping off somewhere, and Jason goes chasing after him. He falls into a giant hole which leads to an underground cavern. To his surprise, he's still all right -- but his pet frog, has mutated due to radiation! Jason eventually stumbles upon a sweet-looking battle-tank, which he claims as his own. The tank is referred to as SOPHIA, which is short for "Subatomic Omni-directional Probative Hyper-responsive Indomitable Abdicator." It's up to the player to guide him with the aid of his new tank through eight stages of underground madness.
As he explores this new world, he will have to defeat a boss for each area. Doing so will grant him a new power -- for example diving underwater -- in the same vein as games like Mega Man. Throughout the course of the game the player must revisit areas multiple times--a cue taken from The Legend of Zelda. The game is notoriously hard and is sometimes mentioned in the same breath as games like Battletoads and Ninja Gaiden.
Jason begins the game in his new tank, and must traverse the area from a side-scrolling perspective. He can do basic things like jump, use special abilities, or fire his gun. He can leave the tank to explore the area around him, but keep in mind that his armor and attacks are severely weaker.
When Jason enters a passageway, the game switches camera-angles to an overhead perspective. He can otherwise shoot up baddies like usual, only without the use of his tank (since SOPHIA can't enter passages or climb ladders). He can throw grenades through a fairly archaic method, and his guns gain power-ups; enabling him to deal more damage, shoot further, and more rapidly.