Mega Man 2 (lsmmega/mm2, and measured in Mesen)

lsmmega's disassembly builds this exact ROM; with the iNES header its header.asm writes in place of the NES 2.0 one, the ROM's SHA-1 is the build's. mega-man-2/rom-is-disassembly

So every line cited from the disassembly is code in the ROM the probes measure.

Cited by: Mega Man 2, Variable jump height

In the standing, walking, running, and landing states, a fresh A press (zjoy1_pressed_bits) copies zjump_speed into Mega Man's vertical speed after the frame's move, so the press frame doesn't lift him. mega-man-2/jump-start

About: Mega Man 2 Jump

The check also switches him to the jumping state, which takes the first step on the next frame (the probe measures 0 px on the press frame, then 5). Walking off a ledge sets the jumping state without a jump (L87-L90; no-coyote-time).

Cited by: Jump, Mega Man 2, Variable jump height

Mega Man's jump speed is $04.$DF, 4.87 px/frame upward, out of water ($05.$80 in water). mega-man-2/jump-speed

About: Mega Man 2 Jump

Value: 1247 1/256 px/frame

1247/256 = 4.87109375 px/frame. The stage start sets the same value (engine/main.asm L199-L202).

Cited by: Jump, Mega Man 2, Mega Man 3, Variable jump height

Gravity takes $40/256 = 0.25 px/frame from Mega Man's upward speed each frame out of water ($1E/256 in water). mega-man-2/gravity

About: Mega Man 2 Gravity

Value: 64 1/256 px/frame²

Cited by: Gravity, Mega Man 2, Variable jump height

_check_object_vertical_move first moves Mega Man by his 8.8 fixed-point speed, positive up, and then subtracts gravity. mega-man-2/motion-order

About: Mega Man 2 Gravity

Subtracting the speed from screen Y moves him up. On landing the routine zeroes the position's fraction (L107-L109), so every jump leaves from a whole pixel.

Cited by: Gravity, Mega Man 2

Falling speed is capped at 12 px/frame ($F4). mega-man-2/max-fall

About: Mega Man 2 Gravity

Value: -12 px/frame

Cited by: Gravity, Mega Man 2, Variable jump height

In the jumping state, with A not held, _run_megaman_jumping drops an upward speed of 2 px/frame or more to exactly 1 px/frame. mega-man-2/release-cap

About: Mega Man 2 Variable jump height

Value: 256 1/256 px/frame

The test reads only the speed's whole byte, so 1.00-1.99 px/frame passes untouched. It runs on every rising frame without A, not only the release frame.

Cited by: Mega Man 2, Variable jump height

The release cut tests only the speed's whole byte, so it applies at 2 px/frame or more and leaves a slower rise alone. mega-man-2/release-threshold

About: Mega Man 2 Variable jump height

Value: 512 1/256 px/frame

Cited by: Mega Man 2, Variable jump height

_run_megaman_jumping checks the release after the frame's move and gravity, so the capped speed first moves Mega Man on the next frame. mega-man-2/release-order

About: Mega Man 2 Variable jump height

Cited by: Mega Man 2, Variable jump height

Gravity brings the 4.87 px/frame take-off under 2 px/frame on frame 13, so letting go of A after 12 frames changes nothing. mega-man-2/release-window

About: Mega Man 2 Variable jump height

Value: 12 frames

Frame 1 is the press frame.

Cited by: Mega Man 2, Variable jump height

Measured in the game, Mega Man's jump peaks at 8 px on frame 5 when A is tapped and at 50 px on frame 19 when it is held 12 frames or more, landing on frames 15 and 41. mega-man-2/apex-by-hold

About: Mega Man 2 Variable jump height

{
 "tap": {
  "apex": 8,
  "apexAt": 5,
  "airtime": 15
 },
 "full": {
  "apex": 50,
  "apexAt": 19,
  "airtime": 41
 },
 "byHold": {
  "1": {
   "apex": 8,
   "apexAt": 5,
   "airtime": 15
  },
  "2": {
   "apex": 12,
   "apexAt": 5,
   "airtime": 18
  },
  "3": {
   "apex": 17,
   "apexAt": 7,
   "airtime": 20
  },
  "4": {
   "apex": 21,
   "apexAt": 8,
   "airtime": 23
  },
  "6": {
   "apex": 28,
   "apexAt": 9,
   "airtime": 27
  },
  "8": {
   "apex": 35,
   "apexAt": 12,
   "airtime": 31
  },
  "10": {
   "apex": 40,
   "apexAt": 13,
   "airtime": 34
  },
  "12": {
   "apex": 50,
   "apexAt": 19,
   "airtime": 41
  }
 }
}

Heights are whole pixels of aobject_ycoord above the take-off row; frame 1 is the press frame. Holds of 12 frames or more give the same arc.

Cited by: Mega Man 2, Variable jump height

Each airborne frame, _run_megaman_jumping zeroes Mega Man's horizontal speed, then sets it to the jumping state's 1.3125 px/frame ($01.$50) toward a held Left or Right. mega-man-2/air-speed

About: Mega Man 2 Air control

Value: 336 1/256 px/frame

With neither direction held, the speed stays zero unless he carries a slide from ice (zslip_speed, L168-L195). Running on the ground is row 5, 1.375 px/frame.

Cited by: Mega Man 2

Measured in the game, Mega Man moves 1.3125 px/frame in the air, turns around on the frame the other direction is pressed, and stops on the frame the d-pad is let go. mega-man-2/air-control-measured

About: Mega Man 2 Air control

{
 "air": 336,
 "run": 352
}

On the normal floor of Heat Man's stage.

Cited by: Mega Man 2, Variable jump height

Measured in the game, Mega Man first steps 0.125 px/frame for 7 frames, then runs at 1.375 px/frame. mega-man-2/walk-start

About: Mega Man 2 Running

{
 "step": 32,
 "stepFrames": 7,
 "run": 352
}

Cited by: Mega Man 2

Mega Man gets no grace window after leaving a ledge; a grounded state that finds no floor switches to the jumping state, which looks for a press only on the frame it lands. mega-man-2/no-coyote-time

About: Mega Man 2 Coyote time

A press on the frame he lands does jump, as from any landing (landing).

Cited by: Coyote time, Jump, Mega Man 2, Variable jump height

Mega Man's X is 8.8 fixed point, and his horizontal speed is an 8.8 magnitude that _check_object_horizontal_move adds or subtracts according to the right bit of ztoward. mega-man-2/x-motion-format

About: Mega Man 2 Running

The position is aobject_screen (page), aobject_xcoord (pixel), and aobject_xcoord_fraction (1/256 px), Mega Man's center. A wall hit zeroes the fraction and pushes him out (terrain-box).

Mega Man never accelerates; each frame his state's row of megaman_status_xcoord_speed_table sets the speed outright, 0 standing, 0.125 px/frame on the first step, 1.375 running, 1.3125 jumping, and 0.5 sliding to a stop. mega-man-2/state-speeds

About: Mega Man 2 Running

{
 "standing": 0,
 "step": 32,
 "running": 352,
 "jumping": 336,
 "slide": 128,
 "landingStop": 0,
 "hit": 144
}

States (zmegaman_status): 2 hit, 3 standing, 4 first step, 5 running, 6 jumping, 7 sliding (landing after a run), 8 landing stop. Ice and conveyors add to or replace the speed after the table (_check_conveyor_ice), and a heavy hit zeroes it outside the jumping state; neither is measured here.

A held direction moves standing Mega Man into the first-step state on the same frame; the step becomes a run when its animation reaches frame 1, a released run becomes a slide, and the slide stops at its animation's frame 2 or restarts the first step if a direction is pressed. mega-man-2/ground-states

About: Mega Man 2 Running

Every grounded state runs, in order, the turn, the speed from its table, the horizontal move, the vertical move, and only then its state change and the jump check, so a new state's speed first applies on the next frame, except that standing switches to the first step before setting the speed. zjoy1_pressed is the d-pad held this frame. The slide and the landing stop share _run_megaman_landing; they differ only in speed.

_turn_megaman faces Mega Man toward a held Left or Right at the start of every moving state's frame, and the move direction follows the facing that same frame, so he reverses at full speed with no skid. mega-man-2/turn-instant

About: Mega Man 2 Running

objects_right is bit 6 of the flag byte and of the controller byte, where bit 6 is Left, so the EOR makes the right bit "Left not held". _megaman_status_parameter copies the facing into ztoward on ordinary ground. The jumping state turns him the same way while a direction is held (air-speed).

Measured from a standstill in Heat Man's stage, Mega Man's first step lasts 7 frames, and a released run slides 8 frames at 0.5 px/frame, 4 px in all, before he stands. mega-man-2/ground-measured

About: Mega Man 2 Running

{
 "stepFrames": 7,
 "slideFrames": 8,
 "slide": 128,
 "tapFrames": 3,
 "tapMoves": 4,
 "landingStopFrames": 4,
 "restepFrames": 6
}

The step and slide lengths come from the animation's frame timings, which the probe measures and the movement code only reads (ground-states). The release frame and the frame after a press still use the old state's speed, since the state changes after the move.

Down changes nothing on open ground; of the walking states only _check_shoot_on_ladder reads Up and Down, and only when a ladder is at hand. mega-man-2/down-on-ground

About: Mega Man 2 Running

Mega Man 2 has no crouch or slide move; the slide here is the landing state after a run.

The jump check runs after the frame's move, so the press frame moves at the ground state's speed, and from the next frame the jumping state's 1.3125 px/frame (or nothing, with no direction held) replaces any run. mega-man-2/takeoff-x

About: Mega Man 2 Jump

Nothing carries over from the run except the facing; a jump from the first step moves 0.125 on the press frame.

Mega Man lands into the running state if Left or Right was held on the frame before landing, at 1.375 px/frame from the next frame with no first step, and into the landing-stop state otherwise. mega-man-2/landing

About: Mega Man 2 Jump

The landing frame itself moves at the air speed. From the landing-stop state a held direction starts the first step; with none, he stands at its animation's frame 2 (4 frames in the probe). The landing frame also runs the jump check, which needs a fresh press of A (zjoy1_pressed_bits), so a held A doesn't jump again.

Cited by: Running

Mega Man's position is his center; the floor and ceiling are tested at x−7 and x+7, 12 px below or above it, and walls at x+8 or x−8 at 12 px and 4 px above and 11 px below it. mega-man-2/terrain-box

About: Mega Man 2 Hitbox

{
 "floor": {
  "x": [
   -7,
   7
  ],
  "y": 12
 },
 "ceiling": {
  "x": [
   -7,
   7
  ],
  "y": -12
 },
 "wall": {
  "x": 8,
  "y": [
   -12,
   -4,
   11
  ]
 }
}

Y grows downward; aobject_ycoord is the center. These points are Mega Man's box against the level. Enemies and items test their own per-object distance tables against his center (_object_hit), so he has no separate box of his own for them.

Cited by: Hitbox, Mega Man 2

_tsa_collision turns a test point into a tile: X / 32 and Y / 32 pick a 32 px block of the stage map, bit 4 of X and of Y pick one of its four 16 px tiles, and the tile's top two bits give its kind, background, block, or one of a per-stage pair such as ladder and spike. mega-man-2/tile-lookup

About: Mega Man 2 Hitbox

Value: 16 px

Every collision point Mega Man tests goes through _appearing_block_collision, which checks the appearing blocks of some stages first and otherwise calls _tsa_collision. A point below the screen reads as background. For walls, blocks, conveyors, and ice count as solid (tsa_horizontal_blockset_flags_table); a spike kills unless he is invincible.

Each of Mega Man's grounded and jumping states moves him horizontally first, testing for a wall, then vertically, testing the floor under a fall or the ceiling over a rise, and only then changes state or checks for a jump, so a frame's floor test uses that frame's new X. mega-man-2/collision-order

About: Mega Man 2 Hitbox

Every grounded state runs the same pair in the same order. In the jumping state the speed's sign before the move picks the branch, so a rising Mega Man never tests the floor.

Cited by: Coyote time

On the ground Mega Man keeps a vertical speed of −0.25 px/frame, the gravity applied after each landing's reset, so every grounded frame's vertical move takes him 0.25 px down and tests x − 7 and x + 7 on the row under his feet; ground there puts him back on it with the Y fraction zeroed, and none sends him to the jumping state. mega-man-2/ground-check

About: Mega Man 2 Coyote time

Value: -64 1/256 px/frame

The snap subtracts (Y + 12) mod 16 from Y, which is 0 while he stands on a tile's top, so on flat ground he never moves. The first step, running, and landing states go to the jumping state the same way (_run_megaman_not_landing_common, L144-L148).

Mega Man first counts as airborne on the frame whose move takes both floor points off the ledge; that frame still moves him at the ground state's speed, drops him 0.25 px, and leaves him in the jumping state falling at 0.5 px/frame, so his feet are 0, 0, 1, 2, 3, 5, and 7 px below the ledge on the walk-off frame and the six after. mega-man-2/walk-off

About: Mega Man 2 Coyote time

{
 "drop": 64,
 "v": -128,
 "heights": [
  0,
  0,
  -1,
  -2,
  -3,
  -5,
  -7,
  -9,
  -11,
  -13,
  -16,
  -19,
  -22,
  -26,
  -30
 ]
}

Running right off an edge at X = e, the walk-off frame is the first whose move brings his center's pixel to e + 7, so one column of his 16 px box still overhangs the ledge; walking left, the first to bring it to e − 8 for an edge whose first column is e. At Heat Man's start (e = 256) he runs from X 262.25 to 263.625 on frame 105, Y's fraction goes to $40, and the speed to $FF.$80. From the next frame the jumping state's d-pad rules apply (air-speed), and its fall gains 0.25 px/frame each frame (gravity). Heights are whole pixels, rounded up.

When the horizontal move puts the wall point ahead in a solid tile, _check_object_horizontal_move zeroes Mega Man's X fraction and pushes him back by the point's depth into the tile, so x + 8 ends on the wall's first column moving right and x − 8 on the first column past it moving left; his speed and state are untouched, so he runs in place. mega-man-2/wall-stop

About: Mega Man 2 Hitbox

The wall point is x + 8 or x − 8 at 12 and 4 px above his center and 11 below it (terrain-box), tested toward his facing (ztoward) on every frame, at whatever speed. A ledge 16 px or more above his feet is a wall. Nothing zeroes his speed: each state sets it from its row every frame (state-speeds), so the push repeats while the d-pad is held.

When a falling Mega Man's floor points find a block, _check_object_vertical_move subtracts (Y + 12) mod 16 from his Y, which puts his feet on that 16 px tile's top, zeroes the Y fraction and the vertical speed, then takes one step of gravity from the speed; so a fall of up to 12 px a frame always ends on the top of the tile it meets. mega-man-2/floor-snap

About: Mega Man 2 Jump

A fall is capped at 12 px a frame (max-fall), less than a tile, so the floor point is always in the top tile of the ground it meets. A rising Mega Man doesn't test the floor (collision-order).

A pit has no floor of its own; once Mega Man's Y passes $E8 on the screen, _check_object_vertical_move asks for a downward scroll, and _check_scroll kills him where the stage doesn't scroll down. mega-man-2/pit-death

About: Mega Man 2 Hitbox

The first pit of Heat Man's stage has spikes at the bottom, which kill him on touch (status 0, _check_vertical_collision L176-L183) before he reaches the screen's edge.

When a rising Mega Man's move puts a ceiling point, x − 7 or x + 7 at 12 px above his center, in a block, _check_object_vertical_move zeroes his Y fraction and adds 16 − ((Y − 12) mod 16) to Y, which puts that point on the first row under the block's 16 px tile, then zeroes his speed and takes one step of gravity from it; he stays in the jumping state and falls from the next frame, starting at 0.25 px/frame. mega-man-2/ceiling-hit

About: Mega Man 2 Hitbox

Value: -64 1/256 px/frame

The test runs after the frame's horizontal move, which tested walls at the old Y, so a running jump whose x + 7 rises into a block's corner is knocked down and keeps its air speed rather than being pushed aside (measured: X 156, a block at X 160-175). The release cut is skipped on the hit frame, which changes nothing, since the speed is already falling; a rise already cut to 1 px/frame still meets a block it reaches (measured at 0.5 px/frame). The ceiling points read tile kinds as the floor points do (_check_vertical_collision), so a spike overhead kills him unless he is invincible.

No grounded state tests the ceiling, since each grounded frame leaves Mega Man's vertical speed at −0.25 px/frame (ground-check) and the vertical move tests only the floor at a negative speed; the jump press then sets the jump speed and the jumping state without a test, so a jump always starts under a ceiling, and the rise first meets it on a later frame. mega-man-2/jump-under-ceiling

About: Mega Man 2 Jump

The press frame doesn't move him up (jump-start). A block 16 px above the floor holds his wall points (terrain-box), so he can't stand under one: 32 px is the lowest ceiling he fits under.

Under a block 32 px above the floor, 8 px over his head, a standing jump meets the block on its second rising frame and lands on frame 11, with his feet 0, 5, 8, 8, 8, 7, 6, 5, 3, 1, and 0 px up on frames 1-11. mega-man-2/low-ceiling-hop

About: Mega Man 2 Jump

{
 "heights": [
  0,
  0,
  5,
  8,
  8,
  8,
  7,
  6,
  5,
  3,
  1,
  0
 ]
}

Heights are whole pixels, rounded up, from frame 0 (before the press): 4.87 px up on frame 2 leaves 3.13 px of headroom, and frame 3's 4.62 px takes his top row into the block.