How do you get to the negative world in Super Mario Bros?

The few times it does actually destroy a Hammer Brother, though, it will only award the player 500 points for the first and 800 for the second, instead of the flat 1000 points Hammer Brothers usually award the player when defeated. In World 8-3, due to a programming error, if Mario stomps on a Koopa shell and uses it to hit a Hammer Brother, it will often fail to destroy the enemy. To fix this bug, simply move the 'jsr SmallBBox' to after the dey opcode, which is what this patch does: Moving direction is set to Rightwards, but since the egg has no horizontal movement and the direction is reset when the Spiny enemy spawns, this doesn't mean much. SpinyRte: sty Enemy_MovingDir,x Set moving direction. Sta Enemy_X_Speed,x Set Spiny egg speed to A (00) A=00Ĭmp #$00 Now check if speed is negative. Now the game jumps back to the SetSpSpd subroutine. Sta Enemy_Y_Speed,x and movement force A=00

InitVStf: lda #$00 initialize vertical speed A=00 Lda #$02 set moving direction for left A=02 SetBBox: sta Enemy_BoundBoxCtrl,x set bounding box control here A=09 Oops, jumping to the bounding box subroutine overwrote A! All that work for nothing. SmallBBox: lda #$09 set specific bounding box size control A=09 The A register stores the appropriate speed value. SetSpSpd: jsr SmallBBox set bounding box control, etc. UsePosv: tya put value from A in Y back to A A=SpeedVar Tay otherwise save value in A to Y for nowĪnd #%00000011 get one of the LSFR parts and save the 2 LSBīeq UsePosv branch if neither bits are setĮor #%11111111 otherwise get two's compliment of Y Ldy Player_X_Speed check player's horizontal speedīcs SetSpSpd if moving faster than a certain amount, branch elsewhere Jsr PlayerLakituDiff move enemy, change direction, get value - difference Ldx ObjectOffset get enemy object buffer offset Iny increment Y four bytes for each valueīpl DifLoop loop until all three are written Here's how the Spiny egg's speed is calculated and stored.ĭifLoop: lda PRDiffAdjustData,y get three values and save them This page details bugs of Super Mario Bros.

How do you get to the negative world in Super Mario Bros?