In this hack, Mario's jump has been reduced to one block high - the jump height he had in Donkey Kong. To permit Mario to clear the levels, several changes were made, such as reducing the height of pipes, the addition of bottomless pits to inescapable holes, and lowering the platforms in the sky stages. Only the most necessary changes were made - most of the levels' geography is unaffected.
Being deprived of his mighty jump has transformed Mario's relationship with his foes. Each of the enemies must be treated as a powerful opponent which Mario can no longer vertically elude. A trio of goombas is now a significant threat. A hopping paratroopa is a mighty stomping giant. Eliminating a row of foes with a shell, or performing a three-goomba jump, is suddenly so much more meaningful now. This hack has made us properly realise what those tiny enemies always were - huge and deadly monsters that, from the safety of the air, merely seemed so small. And as for Bowser - confrontations with him now have the ebb and flow of a swordfight, where he baits Mario with his hops and sends Mario retreating with his fire, and where one lightning-fast strike during a moment of opportunity can spell his end.
In counterbalance with the greater difficulty of this hack, and owing to Mario's inability to access most of the ?-blocks now, you now earn a 1UP when you collect 10 coins instead of 100. This has altered the significance and value of free-standing coins. Suddenly, those guarded caches of coins in 2-2 and the bonus caves are much more rewarding. Timing your jumps to seize floating coins in 1-3 and 3-3 reaps more valuable benefits. And, the 10-coin block is now more than just the frivolous instrument of percussive joy that it once was.
The game ends and the Princess is saved at the end of 3-4. This shortening is for a number of reasons. It's not impossible, but still unreasonable, to jump over Spinies in 4-1. The maze in 4-4 is not feasable in this game. And 3-4 is already very, very hard, and feels suitable as a conclusion to this game.