Unfair Mario is less forgiving than regular arcade Mario. There isn't always forewarning about traps, and it isn't obvious what some of them do. That's the cruelty of this game.
Look out for clues as to where there might be traps. There are often signs that indicate a trap is nearby. When you reach a flag, raise it to save your location as a checkpoint. Don't worry, the flag isn't a trap. Playing cautiously is recommended.
Developer
Unfair Mario was developed by Adrian.
Controls
Left and right arrows to move
Up arrow to jump