Super Mario Bros. Simplified is a ROM hack probably designed to streamline the original Super Mario Bros. gameplay. This could include changes to level design, enemy placement, or overall difficulty to create a more accessible experience. The core gameplay would remain the same, but with adjustments to make it easier for players. This is an independent creation by a member of the ROM hacking community.

Super Mario Bros. Simplified

Super Mario Bros. CO OP Christmas Edition 1.3