Mars: the gun changes everything (that's why you earn it)
Mars brought two dangerous things: half gravity and the gun. Gravity was the easy part: you float across twelve tiles and every jump you learned in the first three worlds becomes a lie your muscle memory tells you, which is exactly the point of the game. The gun was a design risk: a rage platformer where you shoot can turn into just another run and gun. The solution: it isn't found, it's earned, ammo is scarce, and the robots guarding it are immune to jumps. Want the weapon? Learn to dodge first. It's the most honest deal in the whole game, so of course I hid it in the most deceitful world. Balancing the robots in one-hour sessions a night, with the house asleep, took a week of evenings: spare time is slow, but it makes you meticulous.