Mega Man 4 (plasticsmoke ca65 disassembly, and the Rev 1 ROM's bytes)

Mega Man 4 takes off at exactly 5 px/frame ($05.$00), up from Mega Man 3's $04.$E5, and a release cuts any rise to a speed of 0 where Mega Man 3 sets 0.25 px/frame downward. Both cut on every rising frame without A. mega-man-4/jump-line

About: Mega Man 4 Variable jump height

{
 "takeoff": 1280,
 "afterRelease": 0
}

The check runs after the frame's move and gravity (JSR L_92C5 at L410), as in Mega Man 2. The ent_var6 flag skips the cut, as Mega Man 3's force_full_jump does.

Cited by: Jump, Mega Man 4, Variable jump height

Mega Man 4's slide keeps Mega Man 3's 2.5 px/frame but moves on 26 frames (a timer of $1A, counted after each move from the set-up frame on) where Mega Man 3's moves on 21 (a timer of 20). Its A test runs on every slide frame, the set-up's included: a fresh A press without Down jumps out whenever he has headroom, where Mega Man 3 waits for its 9th frame, and A with Down held keeps sliding. The set-up's own press comes with Down, and A held from it into the second frame is no fresh press, so the earliest jump out comes on the slide's 3rd frame. mega-man-4/slide-line

About: Mega Man 4 Ground slide

{
 "speed": 640,
 "frames": 26,
 "jumpFromFrame": 3
}

As in Mega Man 3, a turn ends the slide (L504-L508) and a ceiling over his head keeps it going past the timer (L518-L524). This claim's value used to say the jump out comes "from frame 2", the first frame after the set-up; mega-man-5/slide-kept's "frame 1" counts the set-up frame, where the test first runs. Both describe the same code, and neither frame can carry a fresh press without Down, so the earliest jump out in either count is the 3rd frame.

Cited by: Ground slide, Mega Man 4

A B press fires a normal shot and sets the charge counter to 1; each frame B stays held in a state below 4 the counter rises by 1, looping from 100 back to 92. On release, a counter under 32 ($20) fires nothing more, 32 or more fires a half-charged shot, and 92 ($5C) or more a full one. mega-man-4/charge-shot

About: Mega Man 4 Charge shot

{
 "half": 32,
 "full": 92
}

Charging runs only with the Mega Buster selected (L49-L51). The counter starts at 1, so the half charge comes 31 held frames after the press and the full one 91, if every frame counts; not yet measured.

Cited by: Charge shot, Mega Man 2, Mega Man 4

Mega Man 4 keeps Mega Man 3's knockback, 0.5 px/frame ($00.$80) against his facing under gravity until the hurt animation reaches 9, with no push when the hit lands during a slide. mega-man-4/knockback

About: Mega Man 4 Knockback

{
 "back": 128
}

Both set a 60 ($3C) countdown when the hurt state ends (Mega Man 4 L833-L835); the atlas has checked in Mega Man 3 only that it gates damage.

Cited by: Knockback, Mega Man 4

One routine, entity_player_collide, moves Mega Man vertically in every state: by the sign of his speed's whole byte it moves him down or up by the speed (8.8 fixed point, positive up), takes gravity off the speed, and only then tests the floor points under a fall or the ceiling points over a rise. The ground, air, and slide states all run it before their horizontal move, so a frame's floor and ceiling tests use the X the frame started with and its wall test the new Y. mega-man-4/motion-order

About: Mega Man 4 Jump physics

Mega Man 2 runs the horizontal move first in each state (mega-man-2/collision-order). A speed of exactly 0 counts as rising, so the frame after a release cut (jump-line) moves 0 and tests the ceiling.

Gravity takes $40/256 = 0.25 px/frame from Mega Man's upward speed every frame; the stage start writes $40 to gravity ($99). mega-man-4/gravity

About: Mega Man 4 Jump physics

Value: 64 1/256 px/frame²

Water doesn't change the value for the player: a water timer ($43, set to 3 on entering water) skips gravity for its first frames (L616-L621). The $15 in the stage start's comment is written only by a water enemy's own routine (bank3B L_A870), which puts $40 back after its move.

When gravity takes Mega Man's speed below -7 px/frame (its whole byte under $F9), the gravity routine sets it to exactly $F9.$00, so he falls at most 7 px a frame. mega-man-4/fall-cap

About: Mega Man 4 Jump physics

Value: -1792 1/256 px/frame

Mega Man 3 also caps at $F9 (mega-man-3/jump-line), and Mega Man 2 at 12 px/frame (mega-man-2/max-fall). Mega Man 6 stops only the whole byte, so its fall creeps past 7 (mega-man-6/fall-limits). Mega Man 4's fall reaches the cap 24 frames after a fall from rest begins at −1 px/frame (computed).

On the ground Mega Man's vertical speed rests at -1 px/frame ($FF.$00), which every landing and every floor contact sets through entity_stop_y. So each grounded frame moves him 1 px down, takes gravity, and tests his floor points one row lower; ground there puts him back on it at the same speed, and none leaves him in the air, falling at 1.25 px/frame from the next frame. mega-man-4/ground-check

About: Mega Man 4 Jump physics

Value: -256 1/256 px/frame

Mega Man 3 rests at $FF.$C0 (-0.25 px/frame, mega-man-3/release-cut) and Mega Man 2 at -0.25 too (mega-man-2/ground-check). In Mega Man 4 the same $FF00 rests every entity (mega-man-code-lineage/mm3-mm4-plain-movers).

When a falling Mega Man's floor points find a solid tile, align_down subtracts the tested row's depth into its 16 px tile from his Y pixel, which puts the points on the tile's top row and his feet on its top, and keeps the Y fraction; the speed goes back to -1 px/frame. A fall of up to 7 px a frame always ends on the top of the tile it reaches. mega-man-4/floor-snap

About: Mega Man 4 Jump physics

Mega Man 2 zeroes the Y fraction on landing (mega-man-2/floor-snap); Mega Man 4 keeps it, so a jump's fraction carries into the next one. From flat ground every jump lands with fraction 0, since 5 px/frame and 0.25 px/frame² leave a whole number at each landing (computed).

Mega Man's position is his center. Standing, walking, and in the air his floor points are 12 px below it at x-7, x, and x+7; his ceiling points 9 px above it at x-7 and x+7; and his wall points 8 px to the side he moves toward, at 8 px above, level with, and 11 px below his center. mega-man-4/terrain-box

About: Mega Man 4 Jump physics

{
 "floor": {
  "dy": 12,
  "dx": [
   -7,
   0,
   7
  ]
 },
 "ceiling": {
  "dy": -9,
  "dx": [
   -7,
   7
  ]
 },
 "wall": {
  "dx": 8,
  "dy": [
   -8,
   0,
   11
  ]
 }
}

With the floor points on the row under his feet, the wall points cover the 20 rows from his feet up and the ceiling points sit on the 21st; Mega Man 2 tests 24 rows (mega-man-2/terrain-box). Each test ORs the types of its points, and bit 4 of a type is solid.

When the horizontal move puts a wall point in a solid tile, the move routine pushes Mega Man back by the point's depth into that 16 px tile, so x+8 ends on the wall's first column moving right and x-8 on the first column past it moving left; the X fraction, his speed, and his pose stay, so he walks in place against it. mega-man-4/wall-stop

About: Mega Man 4 Jump physics

Mega Man 2 also zeroes the X fraction at a wall (mega-man-2/wall-stop). A slide tests its own wall points (slide-box).

Because the ground state tests the floor before it moves him, Mega Man walks one frame past the edge before he falls: the frame whose move takes all three floor points off a ledge still counts as grounded, and on the next the floor test finds nothing after a 1 px drop, so he leaves the ground falling 1.25 px/frame and that frame moves him by the air's rules. His feet are then 1, 2, 3, 5, 7, and 9 px below the ledge on that frame and the five after (computed). mega-man-4/walk-off

About: Mega Man 4 Coyote time

{
 "heights": [
  1,
  2,
  3,
  5,
  7,
  9
 ],
 "v": -320
}

The heights are the model's (src/widgets/platformer/mega-man-4.model.ts); the atlas hasn't measured a walk-off in the cartridge.

Mega Man 4 gives no grace jump off a ledge. The ground state reads A only after the air routine reports him standing, and the air state never reads it, so a press on the frame the floor test first fails, or on any later frame of the fall, doesn't jump. mega-man-4/no-coyote-time

About: Mega Man 4 Coyote time

A press on the frame whose move carries him off the edge still jumps, because that frame's floor test ran before the move (walk-off).

When a rising Mega Man's move puts a ceiling point, x-7 or x+7 at 9 px above his center, in a solid tile, entity_align_to_tile adds 16 minus the point's depth into the tile to his Y pixel, which puts the point on the row under the tile, and entity_stop_y sets his speed to -1 px/frame; he stays in the air and falls from the next frame. mega-man-4/ceiling-hit

About: Mega Man 4 Jump physics

Value: -256 1/256 px/frame

The rising branch returns carry clear even after a hit, so the air routine runs on: the release test sees a falling speed and skips the cut, and the frame's horizontal move follows. Mega Man 2 instead leaves the speed at -0.25 after a hit (mega-man-2/ceiling-hit).

Nothing tests the ceiling before a jump starts: a fresh A press on the ground sets the jump speed and runs the air routine, whose rise is the first test. On tile floor the lowest ceiling he can walk under is 32 px up, 11 px over his ceiling points, so a jump there rises 5 px and then 4.75 px on its first two frames and meets the block on the 3rd, which turns it into a fall. mega-man-4/jump-under-ceiling

About: Mega Man 4 Jump physics

A block whose bottom is 16 px over the floor stops him with its wall points (terrain-box), so a ceiling 32 px up is the lowest he walks under; there the press frame lifts his ceiling points to 26 px and the second to 30.75, and the third frame's rise meets it. Only off the tile grid, on a platform entity, could the press frame itself meet a ceiling.

A jump moves Mega Man on its press frame. The ground state has already run the air routine and found the floor; the A press sets 5 px/frame and runs the air routine again, which lifts him 5 px and moves him by the air's rules, so the ground's own walk doesn't run that frame. Measured in Mesen from power-on, standing where he lands at the start of Skull Man's stage, a jump's first frame raised his Y by exactly 5 px. mega-man-4/takeoff

About: Mega Man 4 Variable jump height

{
 "rise": 5,
 "peak": 52.5,
 "peakFrame": 20,
 "airFrames": 40
}

Mega Man 2 sets its speed on the press frame but moves him from the next (mega-man-2/jump-start). The held jump's height is 21 × 5 − 0.25 × 210 = 52.5 px (computed from jump-line and gravity).

Mega Man walks and moves through the air at the speed held in his X speed (ent_xvel), 1.30 px/frame ($01.$4C) on ordinary floor; no walking or air code sets it. The slide writes 2.5 px/frame there, and its end and the jump out of it write $01.$4C back. Measured in Mesen from power-on, at the start of Skull Man's stage, the X speed read $01.$4C and each walking frame moved him 332/256 px. mega-man-4/walk-speed

About: Mega Man 4 Running

Value: 332 1/256 px/frame

332/256 = 1.296875 px/frame, Mega Man 3's walking speed too (mega-man-3/walk-speed).

On the ground Mega Man's sprite sub-type decides whether he moves. Standing ($01), a held direction sets the pause pose ($0D) and moves him one frame; in the pause pose he doesn't move until its animation advances, and then walks ($04) toward a held direction, or stands with none. Walking, the same direction keeps him moving; letting go puts him in the pause pose without a move, and the other direction does too, with one frame's move the new way. mega-man-4/ground-states

About: Mega Man 4 Running

Sub-types $05, $0E, and $0F are the same poses with the shot's offset added ($33), and the code treats them alike. A press of A or Down+A on the ground is handled before any of this, in any pose.

The pause pose lasts 6 frames: its animation (sub-type $0D in bank $0D) holds its first frame for 6 animation ticks, one a frame. So from standing, or on a turn, a held direction moves Mega Man on the first frame, holds him still on the next 5, and walks from the 7th; letting go of a walk holds him for 6 frames, whatever the d-pad does, before he stands or walks on. Measured in Mesen from power-on, at the start of Skull Man's stage, Right moved him on frame 1, not on frames 2 to 6, and on every frame from 7 to 40; letting go on frame 41 kept him still in the pause pose on frames 41 to 46, and he stood from frame 47. mega-man-4/ground-measured

About: Mega Man 4 Running

{
 "pauseFrames": 6
}

Mega Man 6 holds a 5-frame halt after the first step too (mega-man-6/walk-start), from a counter, not an animation.

Every frame in the air the d-pad alone sets where Mega Man moves: the air routine copies the held Left or Right into his direction and moves him by his X speed that way, 1.30 px/frame, and with neither held he doesn't move. He turns at once, and nothing carries over from the ground. mega-man-4/air-speed

About: Mega Man 4 Air control

Mega Man 2 sets a separate air speed, 1.3125 px/frame (mega-man-2/air-speed).

The frame a falling Mega Man's floor test finds ground puts him in the ground state with the walking pose ($04), and still moves him by the air's rules. On the next frame he walks on at once if he holds the direction he held on landing; none starts the pause pose, and the other direction starts it with one move that way, as a turn does. The air state reads no A press, so a press on the landing frame is lost, and the next frame's press jumps. mega-man-4/landing

About: Mega Man 4 Jump physics

Mega Man 2 instead lands running or into a landing stop (mega-man-2/landing).

Down and a fresh A press start a slide only if the slide's start point, 15 px ahead of his center and 4 px below it, isn't in a wall; with a wall there the press does nothing, neither slide nor jump. The slide moves his Y pixel 2 px down and tests a lower, wider box: floor points 10 px below the new center at x-14, x, and x+14, and wall points 15 px ahead, level with it and 9 px below. With no floor under those points, ground 16 px below the center keeps the slide going, and none stands him up. mega-man-4/slide-box

About: Mega Man 4 Ground slide

{
 "lower": 2,
 "floor": {
  "dy": 10,
  "dx": [
   -14,
   0,
   14
  ]
 },
 "ceiling": {
  "dy": 0,
  "dx": [
   -14,
   0,
   14
  ]
 },
 "wall": {
  "dx": 15,
  "dy": [
   0,
   9
  ]
 },
 "start": {
  "dx": 15,
  "dy": 4
 },
 "headroom": {
  "dy": -14,
  "dx": [
   -14,
   0,
   14
  ]
 },
 "below": {
  "dy": 16,
  "dx": [
   -14,
   0,
   14
  ]
 }
}

The floor points stay on the same row, so on flat ground his feet don't move, and the slide box's wall points cover the 10 rows over his feet. Mega Man 3 lowers him 2 px too (mega-man-3/slide). His Y pixel stays 2 px low on the frame he stands up, until the next frame's floor test puts him back.

A slide ends in two ways. When the slide box finds no floor and no ground 16 px below his center either (slide-box), he stands up at once, with no headroom test, before that frame's A test and move. Otherwise it ends at the standing test, which a wall, the timer's end, or a turn sends it to. A turn (a held direction against the slide's) zeroes the timer and still moves him 2.5 px the new way on that frame. The test checks his standing headroom, three points 14 px above the slide's center (12 px above his standing one) at x-14, x, and x+14: a solid tile there keeps him sliding at 2.5 px/frame, testing again each frame, and otherwise he stands up in the walking pose, at walking speed, after that frame's move. A fresh A press without Down jumps out of it instead, at 5 px/frame and walking speed, if the same headroom is clear, from the 2 px lower slide center; the earliest such press comes on the slide's 3rd frame (slide-line). mega-man-4/slide-exit

About: Mega Man 4 Ground slide

The stand-up leaves his walk direction ($31) as the slide's, so a direction held the same way walks on the next frame without the pause. A platform entity overhead blocks the jump and the stand-up too (L_83F2), which the lab doesn't model.

Mega Man 4's movement on ordinary floor differs from Mega Man 3's in five numbers. The first is the jump's take-off speed: 5 px/frame ($05.$00) against Mega Man 3's 4.89 ($04.$E5). The second is the speed on the ground and after a landing: -1 px/frame ($FF.$00) against -0.25 ($FF.$C0). Third, a release cuts a rise to 0, where Mega Man 3 sets the same -0.25. Fourth, the slide timer starts at 26 ($1A) against 20 ($14), so the slide moves on 26 frames against 21 (slide-line, mega-man-3/slide). Fifth, Mega Man 4 tests for the jump out of a slide on every slide frame, where Mega Man 3 skips the test while the timer is 12 ($0C) or more, so the earliest jump out comes on the 3rd frame against the 9th. mega-man-4/movement-differs-from-mega-man-3

About: Mega Man 4 Jump physics

{
 "takeoff": 1280,
 "other": 1253
}

The two games share the walk and air speed (1.30 px/frame), the slide's 2.5 px/frame, gravity of 0.25 px/frame², and the 7 px/frame fall cap; each set's own claims quote them (mega-man-4/walk-speed, slide-line, gravity, fall-cap; mega-man-3/walk-speed, slide, jump-line). The walk's pause and the box were not compared here.

Cited by: Mega Man (classic series)