Game Logic Functions

Some time ago I heard a quote that went something like: “In game development, all concerns are cross-cutting.” I’ve long since lost the exact quote and have no way of tracking down the source, but it’s a statement that’s stuck with me. This game has a number of functions that don’t fit neatly into a particular subsystem, and don’t implement a specific enough functionality to be an entire topic of examination. Rather, this page contains a jumble of functions that I couldn’t think of a better home for.

GameRand()

The GameRand() function returns a pseudorandom number based on a fixed table of randomness combined with influence from the player and scrolling game window positions. The output sequence from this function is deterministic for a given sequence of player and scroll positions. This is necessary for consistency during demo playback – without a reproducible sequence of random values the actors would desynchronize from the recorded player movements.

randStepCount is reset to zero each time a level is (re)started (see InitializeMapGlobals()), which provides the basis of this predictable output assuming the player follows the exact same path through the map each time.

Functionality that does not affect demo synchronization should ideally use the standard rand() function or the Borland-specific random() macro, but not everything does. (e.g. sprite drawing in ActTransporter, sound effect choice in DestroyBarrel()).

word GameRand(void)
{
    static word randtable[] = {
        31,  12,  17,  233, 99,  8,   64,  12,  199, 49,  5,   6,
        143, 1,   35,  46,  52,  5,   8,   21,  44,  8,   3,   77,
        2,   103, 34,  23,  78,  2,   67,  2,   79,  46,  1,   98
    };

    randStepCount++;
    if (randStepCount > 35) randStepCount = 0;

    return randtable[randStepCount] + scrollX + scrollY + randStepCount +
        playerX + playerY;
}

randtable[] is a 36-element array of random-ish numbers of unknown origin. On each call, the global randStepCount is incremented to select the next element of the table. The very first call skips over index zero, but after that all elements from index zero to 35 are rotated through.

The return value is the sum of:

I sat for a while and analyzed this function to try to determine what its range of outputs was. The highest value would occur on a 1,024 × 32 map with both the player (1,021, 31) and scroll position (986, 14) as far to the bottom right as possible. The maximum random table value is “233” at index three, so the sum of everything is 2,288. That’s the maximum plausible value.

The minimum is not really dependent on the map dimensions, and occurs when the player (0, 4) and scroll position (0, 0) are both at the top left. The minimum random table value isn’t actually relevant, as it’s the sum of the table value and its index within the table that is used. The smallest combination from the table is the value “12” at index one. This places the minimum plausible value at 16.

This function is cryptographically laughable, but even for the purposes of gameplay it’s not terribly robust. It’s quite easy for the player to stand still for a moment and observe actors that seem to be “stuck” in one branch of their decision-making. By nudging the player (or the view) one or two tiles, the actors will regain their senses and start behaving in a more interesting way. That’s caused by this random number generator producing repetitive output which is being consumed by the same group of actors in sequence.

IsTouchingPlayer()

The IsTouchingPlayer() function returns true if the passed sprite_type and frame located at x_origin and y_origin is touching any part of the player sprite at its current position. This function is very similar to IsIntersecting(), but this function only accepts one sprite; the other sprite is implicitly the player at playerX and playerY.

bool IsTouchingPlayer(
    word sprite_type, word frame, word x_origin, word y_origin
) {
    register word height, width;
    word offset;

    if (playerDeadTime != 0) return false;

If the player has died but their sprite is still on the map (e.g. during the angel death animation) they are incapable of touching anything. Nonzero playerDeadTime represents this, which causes an early false return.

    offset = *(actorInfoData + sprite_type) + (frame * 4);
    height = *(actorInfoData + offset);
    width = *(actorInfoData + offset + 1);

The caller passed a sprite_type and a frame, but what is actually needed is the width and height of that sprite. This needs to be looked up in the tile info data for the actor sprites.

All tile info in memory begins with a lookup table, which contains one 16-bit value per sprite type. The value read from this position is an offset to the tile info for frame zero for that sprite type. Frame zero, and all subsequent frames beyond, contain a four-word structure of height, width, image data offset, and image data segment. Arbitrary frames can be selected by stepping past frame zero in four-word increments.

The assignment to offset uses the above addressing math to produce an offset, in words, where the actorInfoData record for frame of sprite_type can be found. By adding this offset to the actorInfoData pointer and dereferencing it, the height of the sprite is found. width is calculated similarly, adding one to the offset to address the next field in the structure.

    if (
        x_origin > mapWidth && x_origin <= WORD_MAX &&
        sprite_type == SPR_EXPLOSION
    ) {
        width = x_origin + width;
        x_origin = 0;
    }

When the sprite_type is SPR_EXPLOSION, we might have to deal with an edge condition (literally). Some explosion origins can occur off the left edge of the screen, having a conceptually negative X that looks like a large positive number in the unsigned math the game uses. There is identical code (and a more satisfying explanation) in IsIntersecting().

    if ((
        (playerX <= x_origin && playerX + 3 > x_origin) ||
        (playerX >= x_origin && x_origin + width > playerX)
    ) && (
        (y_origin - height < playerY && playerY <= y_origin) ||
        (playerY - 4 <= y_origin && y_origin <= playerY)
    )) return true;

    return false;
}

The intersection is a large set of nested expressions, with horizontal tests first followed by vertical tests.

Horizontally, when the player’s left column is to the left of (or aligned with) the sprite’s left column, intersection happens if the empty space to the right of the player (playerX + 3) is to the right of the sprite’s left column. In the opposite order, when the player’s left column is to the right of (or aligned with!) the sprite’s left column, intersection could also happen if the player’s left column is to the left of the empty space to the right of the sprite (x_origin + width).

Vertically, when the player’s bottom row is higher than (or aligned with) the sprite’s bottom row, intersection happens if the player’s bottom row is lower than the empty space above the sprite (y_origin - height). In the opposite order, when the player’s bottom row is below (or aligned with!) the sprite’s bottom row, intersection could also happen if the top row of tiles for the player (playerY - 4) is higher than (or aligned with) the sprite’s bottom row.

If at least one horizontal and one vertical test passes, the return value is true. Otherwise false is returned.

HurtPlayer()

The HurtPlayer() function deducts a bar of health from the player, and kills them if they have lost enough health. This function unconditionally causes the player to release any active cling, and may show an “Ouch!” speech bubble or the pounce hint if either of those things has not happened before.

Each time this function is called, a 44-tick cooldown interval starts in which the player cannot be hurt again.

void HurtPlayer(void)
{
    if (
        playerDeadTime != 0 ||
        isGodMode ||
        blockActionCmds ||
        activeTransporter != 0 ||
        isPlayerInvincible ||
        isPlayerInPipe ||
        playerHurtCooldown != 0
    ) return;

There are a whole bunch of things that could occur in the game that make the player momentarily invincible:

  • When playerDeadTime is nonzero, the player has already lost enough health to kill them, and they are now experiencing the death animation sequence before the level restarts. There is no reason to hurt a player that’s already dead.
  • A true value in isGodMode means the user has enabled the F10 + G debug key to enable “god mode.” This shields the player from all injury except for falling off the map, which is not something this function deals with.
  • blockActionCmds is enabled while the player is inside a creature like the Tulip Launcher Plant. They effectively no longer exist on the map while this is true.
  • activeTransporter is nonzero when the player has entered one Transporter and is waiting to come out of the other one. The player should not be able to take damage during this time.
  • The isPlayerInvincible flag is true as long as the player has an Invincibility Sphere protecting them. The flag becomes false once the bubble expires.
  • The isPlayerInPipe flag is true while the player is inside of a pipe system. They should be protected from outside injury while moving across the map.
  • playerHurtCooldown is nonzero for a short time after a previous call to this function. The player sprite flashes during this time, and when it returns to zero the player is able to be injured again.

Each of these conditions disqualifies the player from taking damage, so an early return bypasses the rest of this function.

    playerClingDir = DIR4_NONE;

When the player is injured, clings are unconditionally released by setting playerClingDir to DIR4_NONE.

    if (!sawHurtBubble) {
        sawHurtBubble = true;

        NewActor(ACT_SPEECH_OUCH, playerX - 1, playerY - 5);

        if (pounceHintState == POUNCE_HINT_UNSEEN) {
            pounceHintState = POUNCE_HINT_QUEUED;
        }
    }

If this is the first time the player has been injured since the level started, the sawHurtBubble flag will be false and this block executes. The flag is then set to prevent this from occurring again.

NewActor() inserts a “Speech Bubble: Ouch!” (ACT_SPEECH_OUCH) at the player’s position. The bubble is five tiles wide, relative to the player’s three, so the X position is adjusted by -1 to center it. The Y position is five tiles above the player’s feet.

The pounceHintState system is a little convoluted, but it holds the value POUNCE_HINT_UNSEEN when the episode begins. If it’s still in that state when the player is hurt, it’s updated to POUNCE_HINT_QUEUED which (eventually, in GameLoop()) shows the one-time “pounce hint” dialog. This never happens again over the course of an episode, even going so far as to be stored as a field in the saved games.

    playerHealth--;

    if (playerHealth == 0) {
        playerDeadTime = 1;
        scooterMounted = 0;
    } else {
        UpdateHealth();
        playerHurtCooldown = 44;
        StartSound(SND_PLAYER_HURT);
    }
}

One point is deducted from playerHealth, then the updated value is tested to see if that has killed the player.

If playerHealth became zero, the player died and playerDeadTime is set to one, beginning the death animation. The player is force-removed from any scooter they may be riding on by setting scooterMounted to zero.

Otherwise, the damage was not fatal, and UpdateHealth() is called to redraw the health area in the status bar with the new health count. playerHurtCooldown is set to 44, giving the player some time to retreat from the danger before getting hurt again. StartSound() also occurs here, queuing the SND_PLAYER_HURT warning.

ProcessAndDrawPlayer()

The ProcessAndDrawPlayer() function determines the player’s reaction to pain or death and draws the player sprite accordingly. This function is also responsible for determining if the player has fallen to their death in a bottomless pit. If the player has died and completed the relevant death animation sequence, this function reloads the game state to the way it was when the level was last started and returns true. If the level has not been restarted, this function returns false.

The player can die in two distinct ways:

  • When touching a dangerous object, HurtPlayer() deducts one unit of health. Once all the available health has been depleted, HurtPlayer() sets playerDeadTime to 1. This marks the player as “dead” and changes the player sprite into an angel that no longer responds to user input or objects on the map. After a short delay the angel rises off the top of the screen and the level restarts.
  • If the player falls into a bottomless pit, the playerY value will leave the bottom of the map data and enter undefined and buggy space. Once they fall sufficiently far, this function sets both playerDeadTime and playerFallDeadTime to 1. The player falls completely off the bottom edge of the screen, a speech bubble rises up from the point where they fell from, and the level restarts.

This function is conceptually a wrapper around DrawPlayer() and makes the final decision about which sprite frame to show at any given time. Once the player dies, this function becomes responsible for controlling the position – regular keyboard/joystick input and movement rules no longer apply.

bbool ProcessAndDrawPlayer(void)
{
    static byte speechframe = 0;

speechframe is a function-local variable that maintains its value across calls for the lifetime of the program’s execution. This variable is used to rotate through five possible frames of a speech bubble sprite that appear when the player falls into a bottomless pit.

    if (maxScrollY + SCROLLH + 3 < playerY && playerDeadTime == 0) {
        playerFallDeadTime = 1;
        playerDeadTime = 1;

        if (maxScrollY + SCROLLH + 4 == playerY) {
            playerY++;
        }

        speechframe++;
        if (speechframe == 5) speechframe = 0;
    }

playerDeadTime must be zero for this block to execute at all, which prevents an already-dead player from suffering the indignity of falling out of the map and dying again.

maxScrollY represents the row of map tiles that is drawn at the top of the screen when the view is scrolled down to the lowest visible area of the map. Adding SCROLLH yields the first row after the end of the visible map data, effectively the first row of map tiles that the status bar covers. Adding three to that running total covers four – but not all five – of the tiles of height the player sprite has. playerY becomes greater than this as soon as the top row of player sprite tiles falls behind the status bar.

Once the player has fallen completely out of view, they are dead. playerFallDeadTime is set to 1 to begin the falling death animation, and playerDeadTime is also set to 1 to inform the rest of the game’s functions that they no longer need to test for the player interacting with any surfaces or objects.

The off-screen math is repeated with a strict equality check instead of an inequality, this time against four. The intention is for there to be a one-tile gap between the bottom of the visible map area and the top of the player sprite. If the player was falling at a slow speed, the only way to obtain a sufficient gap is to increase playerY again.

Once playerY reaches this point off the screen, it no longer increases. There is no need for the player to continue falling if nothing can see them anyway.

speechframe is incremented to select the next speech bubble message out of a rotation of five available frames.

    if (playerFallDeadTime != 0) {
        playerFallDeadTime++;

        if (playerFallDeadTime == 2) {
            StartSound(SND_PLAYER_HURT);
        }

        for (; playerFallDeadTime < 12; playerFallDeadTime++) {
            WaitHard(2);
        }

The previous if ends and a new one begins. This one handles the animation sequence of the player falling into the bottomless pit.

In the case where the player was just found to have fallen out of the map, playerFallDeadTime will be 1 which then immediately increments to 2 upon entry here. That, in turn, passes the next if and StartSound() plays SND_PLAYER_HURT. It also passes the condition in the for loop, which takes playerFallDeadTime up to 12 after all iterations finish. Each iteration calls WaitHard() for an inescapable 2 timer ticks producing a total delay of 1 ⁄ 7 of a second. This pauses everything in the game – the game loop stops cold while this delay is running – causing a noticeable “hitch” as the player falls.

It’s also important to remember that this is occurring during the same game tick where the player first moved off the map. The video frame for this tick isn’t done yet, and the screen is still showing the previous frame where the top of the player’s head is still in view.

I liked it better the other way.

This looks like maybe it was a late addition to speed up the animation. Removing the for loop removes the delay hitch and lets the player fall for a little under a second before the speech bubble comes. It actually feels pretty nice that way; I don’t know why they hacked it shorter this way.

Once playerFallDeadTime reaches 12 nothing else in here runs until this function is called on the next game tick.

        if (playerFallDeadTime == 13) {
            StartSound(SND_PLAYER_DEATH);
        }

        if (playerFallDeadTime > 12 && playerFallDeadTime < 19) {
            DrawSprite(
                SPR_SPEECH_MULTI, speechframe,
                playerX - 1, (playerY - playerFallDeadTime) + 13,
                DRAW_MODE_IN_FRONT
            );
        }

Once playerFallDeadTime reaches 13, StartSound() plays the SND_PLAYER_DEATH effect.

The for loop begins as well, and runs over the next six game ticks. During each one, DrawSprite() places the speech bubble SPR_SPEECH_MULTI sprite using speechframe to select the message contained within. This is drawn centered against the last known playerX and rising up from playerY into the bottom of the visible screen. DRAW_MODE_IN_FRONT ensures that nothing on the map will cover up the bubble.

        if (playerFallDeadTime > 18) {
            DrawSprite(
                SPR_SPEECH_MULTI, speechframe,
                playerX - 1, playerY - 6, DRAW_MODE_IN_FRONT
            );
        }

When playerFallDeadTime exceeds 18, the speech bubble stops rising and becomes fixed at a point six tiles above playerY. Given that the player is five tiles tall and the code earlier in this function ensured a one-tile gap between the bottom row of visible map tiles and the top of the player sprite, this speech bubble should be fixed at the bottom of the game window now. It will be drawn here during every subsequent game tick until the level restarts.

        if (playerFallDeadTime > 30) {
            LoadGameState('T');
            InitializeLevel(levelNum);
            playerFallDeadTime = 0;
            return true;
        }

When playerFallDeadTime exceeds 30, the animation is over and the level should be restarted. LoadGameState() reloads the game state from the temporary save file in the 'T' slot, InitializeLevel() reloads and resets all of the map state to play levelNum, and playerFallDeadTime is reset to zero (gratuitously; InitializeLevel() called InitializeMapGlobals() which did that already).

With the map reloaded, this function needs to return true to inform its caller (GameLoop()) that there is a discontinuity in the game state and it should not continue trying to draw the frame it had been working on – it needs to start all over.

    } else if (playerDeadTime == 0) {
        if (playerHurtCooldown == 44) {
            DrawPlayer(
                playerBaseFrame + PLAYER_PAIN, playerX, playerY,
                DRAW_MODE_WHITE
            );
        } else if (playerHurtCooldown > 40) {
            DrawPlayer(
                playerBaseFrame + PLAYER_PAIN, playerX, playerY,
                DRAW_MODE_NORMAL
            );
        }

        if (playerHurtCooldown != 0) playerHurtCooldown--;

        if (playerHurtCooldown < 41) {
            if (!isPlayerPushed) {
                DrawPlayer(
                    playerBaseFrame + playerFrame, playerX, playerY,
                    DRAW_MODE_NORMAL
                );
            } else {
                DrawPlayer(
                    playerPushForceFrame, playerX, playerY, DRAW_MODE_NORMAL
                );
            }
        }

This else if body runs whenever playerDeadTime is zero, and represents the “happy path” of player sprite drawing: The player is not falling off the map, and they are not dead. They may, however, be experiencing pain or an involuntary push in some direction, which selects one of a few DrawPlayer() calls according to this table:

playerHurtCooldownisPlayerPushedDRAW_MODE_…Sprite Frame
0–40falseNORMALplayerBaseFrame + playerFrame
0–40trueNORMALplayerPushForceFrame
41–43—NORMALplayerBaseFrame + PLAYER_PAIN
44—WHITEplayerBaseFrame + PLAYER_PAIN

Each path draws the player at playerX and playerY without modification. Any non-zero value in playerHurtCooldown decrements in the process.

Note:

The DrawPlayer() code considers playerHurtCooldown as a means to flash the player’s sprite. The player is only drawn if playerHurtCooldown is even. This means that the non-white PLAYER_PAIN frame is only visible for a single game tick, which makes it very easy to miss.

playerHurtCooldown also decrements in between the blocks that check for pain versus regular sprite drawing, which effectively jumps from the visible pain state in “playerHurtCooldown = 42” to the visible normal state in “playerHurtCooldown = 40.”

    } else if (playerDeadTime < 10) {
        if (playerDeadTime == 1) {
            StartSound(SND_PLAYER_HURT);
        }

        playerDeadTime++;
        DrawPlayer(
            PLAYER_DEAD_1 + (playerDeadTime % 2), playerX - 1, playerY,
            DRAW_MODE_IN_FRONT
        );

This else if handles the early (but still nonzero) counts of playerDeadTime. Values from 1 to 9 are handled here. The player is recently dead, and should be drawn as a stationary angel in the spot where the fatal hit occurred.

On the first trip through the body here, playerDeadTime will be 1 and StartSound() queues the SND_PLAYER_HURT sound effect for playback. This is necessary because the HurtPlayer() call that killed the player chose not to play its own sound effect.

playerDeadTime increments during each game tick, and DrawPlayer() uses that value modulo 2 to select between two player sprite frames: PLAYER_DEAD_1 and PLAYER_DEAD_2. These two frames show the player dressed as an angel with flapping wings, with DRAW_MODE_IN_FRONT requesting that nothing cover it. The playerX value needs to be adjusted by one because the angel sprite frames are two tiles wider than the regular sprite, and this keeps them centered relative to where the player had been. playerY needs no correction, since the angel’s height is the same as the rest of the frames.

    } else if (playerDeadTime > 9) {
        if (scrollY > 0 && playerDeadTime < 12) {
            scrollY--;
        }

        if (playerDeadTime == 10) {
            StartSound(SND_PLAYER_DEATH);
        }

        playerY--;
        playerDeadTime++;
        DrawPlayer(
            PLAYER_DEAD_1 + (playerDeadTime % 2), playerX - 1, playerY,
            DRAW_MODE_IN_FRONT
        );

Once playerDeadTime reaches 10, the previous branch stops occurring and this one takes over. The player is still dead and still drawn as an angel but now it should rise up off the top of the screen.

When playerDeadTime has values of either 10 or 11 (and assuming scrollY is sufficiently high to support this) the scroll position is adjusted to show additional area at the top of the map. This scrolls everything down on the screen by two tiles, giving the angel a bit more vertical space to rise through before leaving the screen. During the first step, when playerDeadTime is 10, StartSound() queues the SND_PLAYER_DEATH effect.

During every tick, from here until the level restarts, playerY decrements (moving the angel one tile higher on the screen) and playerDeadTime increments. DrawPlayer() draws the sprite exactly how it did in the previous branch when the angel was stationary.

        if (playerDeadTime > 36) {
            LoadGameState('T');
            InitializeLevel(levelNum);
            return true;
        }

Once playerDeadTime exceeds 36, the player sprite is almost certainly off the screen and the level should be restarted. LoadGameState() reloads the game state from the temporary save file in the 'T' slot and InitializeLevel() reloads and resets all of the map state to play levelNum.

With the map reloaded, this function needs to return true to inform its caller (GameLoop()) that there is a discontinuity in the game state and it should not continue trying to draw the frame it had been working on – it needs to start all over.

    }

    return false;
}

In the majority of cases, no path through this function restarts the level and the game loop should continue working on the current frame. false is returned as an indication that everything is normal and nothing in here interfered with the state of the world.

SET_PLAYER_DIZZY()

The SET_PLAYER_DIZZY() macro puts the player into a “dizzy” state, which will begin to take effect the next time they are standing on solid ground. This is structured as a macro to provide a counterpart to the ClearPlayerDizzy() function.

#define SET_PLAYER_DIZZY() { queuePlayerDizzy = true; }

queuePlayerDizzy marks the player as needing to enter the dizzy state, but does not directly place them into such a state. For the player’s dizziness to take effect, they must be standing on the ground. Typically this function will be called while the player is free-falling, and they need to land before queued dizziness becomes actual dizziness.

ProcessPlayerDizzy()

The ProcessPlayerDizzy() function determines when a queued bout of dizziness should become effective, and handles the cases where dizziness wears off naturally or is abruptly canceled.

Dizziness is queued by setting queuePlayerDizzy to true, but other parts of the game respond to the dizzy condition (e.g. by immobilizing the player) by reading playerDizzyLeft. This function bridges the two variables together and manages their lifecycles.

void ProcessPlayerDizzy(void)
{
    static word shakeframes[] = {
        PLAYER_SHAKE_1, PLAYER_SHAKE_2, PLAYER_SHAKE_3, PLAYER_SHAKE_2,
        PLAYER_SHAKE_1, PLAYER_SHAKE_2, PLAYER_SHAKE_3, PLAYER_SHAKE_2,
        PLAYER_SHAKE_1
    };

Dizziness is visualized as a three frame animation sequence of the player’s sprite shaking its head back and forth. The graphics are such that these frames can be looped in a “ping-pong” sequence and look convincing. The shakeframes[] that form the animation are PLAYER_SHAKE_1..3. Also worth noting, these array elements are played in reverse order.

    if (playerClingDir != DIR4_NONE) {
        queuePlayerDizzy = false;
        playerDizzyLeft = 0;
    }

If a pounce is queued while the player is in midair, and they push into a wall to initiate a cling, playerClingDir will take a value that is not DIR4_NONE. This cancels the queued dizzy spell in the same way ClearPlayerDizzy() would – that function’s body is repeated in this if body.

    if (
        queuePlayerDizzy &&
        TestPlayerMove(DIR4_SOUTH, playerX, playerY + 1) != MOVE_FREE
    ) {
        queuePlayerDizzy = false;
        playerDizzyLeft = 8;
        StartSound(SND_PLAYER_LAND);
    }

If queuePlayerDizzy is true, it’s necessary to determine if the player is standing on the ground. (The player can’t experience dizziness while jumping or falling, only standing.) TestPlayerMove() evaluates the map blocks below the player’s feet at playerX and playerY plus one – the player stands on the tiles, not in them – to see if a move is permitted into them in the DIR4_SOUTH direction. If MOVE_FREE is returned, there is air below the player and they can’t be dizzy here.

Otherwise, they are on the ground and the if body runs. queuePlayerDizzy is set to false and playerDizzyLeft becomes eight. Queued dizziness has become actual dizziness.

With a nonzero playerDizzyLeft, the regular MovePlayer function becomes a no-op and is no longer available to play the landing sound effect. So that is done here, with StartSound() queuing SND_PLAYER_LAND.

    if (playerDizzyLeft != 0) {
        playerFrame = shakeframes[playerDizzyLeft];
        playerDizzyLeft--;
        isPlayerFalling = false;

        if (playerDizzyLeft > 8) {
            ClearPlayerDizzy();
        }
    }
}

Whenever playerDizzyLeft is nonzero, the player is dizzy and this state needs to be managed. Visually, the dizzy effect is produced by forcing playerFrame to one of the shakeframes[] values, as selected by playerDizzyLeft. It starts at eight, picking the last element in the array.

playerDizzyLeft is decremented, moving one step closer to having the dizziness wear off.

isPlayerFalling is also cleared here, which is probably a workaround for MovePlayer being disabled and missing the landing event.

The test for playerDizzyLeft greater than eight is most likely cruft. I do not see any way for this condition to ever be true. It looks like the original implementation was built around an incrementing counter, which would call ClearPlayerDizzy() once it incremented to the target maximum.

ClearPlayerDizzy()

The ClearPlayerDizzy() function resets all the global variables related to the player’s “dizziness” immobilization, immediately returning the player to normal state.

void ClearPlayerDizzy(void)
{
    queuePlayerDizzy = false;
    playerDizzyLeft = 0;
}

Normally only one of these variables will need to be reset – queuePlayerDizzy is true when the player is waiting for dizziness to kick in, while playerDizzyLeft is nonzero while the dizziness is actively affecting the player. Nevertheless, both are reset here to immediately cure the dizziness, or to prevent its onset if it has been queued.

AddScoreForSprite()

The AddScoreForSprite() function determines how many points should be added to the player’s score for defeating an actor of a given sprite_type, and adds that amount. The status bar is updated to reflect the new score.

This function does not spawn any floating score effects or other rewards. Its only concern is incrementing the score in the status bar.

void AddScoreForSprite(word sprite_type)
{
    switch (sprite_type) {
    case SPR_JUMPING_BULLET:
        AddScore(800);
        break;

    case SPR_GHOST:
    case SPR_MOON:
    case SPR_SHARP_ROBOT_FLOOR:
    case SPR_SHARP_ROBOT_CEIL:
        AddScore(400);
        break;

The entire function follows this pattern. sprite_type is tested in a large switch, and the matching case is the one that calls AddScore() with the hard-coded number of points. SPR_JUMPING_BULLET gives 800 points, while each SPR_GHOST, SPR_MOON, SPR_SHARP_ROBOT_FLOOR, and so on grants only 400.

Once the points are added, break exits the switch, which also ends the function.

    case SPR_SAW_BLADE:
        AddScore(3200);
        break;

    case SPR_SPEAR:
    case SPR_STONE_HEAD_CRUSHER:
    case SPR_PARACHUTE_BALL:
        AddScore(1600);
        break;

    case SPR_SPARK:
    case SPR_RED_JUMPER:
        AddScore(6400);
        break;

    case SPR_SPIKES_FLOOR:
    case SPR_SPIKES_FLOOR_RECIP:
    case SPR_SPIKES_E:
    case SPR_SPIKES_W:
        AddScore(250);
        break;

    case SPR_SUCTION_WALKER:
    case SPR_SPITTING_TURRET:
        AddScore(1000);
        break;

    case SPR_ROAMER_SLUG:
    case SPR_HINT_GLOBE:
        AddScore(12800);
        break;

    case SPR_PUSHER_ROBOT:
        AddScore(2000);
        break;

    case SPR_ARROW_PISTON_W:
    case SPR_ARROW_PISTON_E:
    case SPR_SPIKES_E_RECIP:
    case SPR_SPIT_WALL_PLANT_E:
    case SPR_SPIT_WALL_PLANT_W:
    case SPR_RED_CHOMPER:
    case SPR_SENTRY_ROBOT:
        AddScore(500);
        break;

    case SPR_DRAGONFLY:
        AddScore(50000L);
        break;

    case SPR_74:
    case SPR_BABY_GHOST_EGG:
    case SPR_EYE_PLANT:
    case SPR_96:
    case SPR_PINK_WORM_SLIME:
    case SPR_BIRD:
        AddScore(100);
        break;

The two odd sprites SPR_74 and SPR_96 are cases that get tested, but never happen. There are no actors in the game that use these sprite types. There are actor types with these numbers (specifically, variants of the Baby Ghost Egg and Eye Plant), but they use sprite types that are already covered by other cases here.

    case SPR_STAR:
    case SPR_CABBAGE:
    case SPR_HEART_PLANT:
    case SPR_BABY_GHOST:
    case SPR_CLAM_PLANT:
    case SPR_84:
    case SPR_PINK_WORM:
    case SPR_ROCKET:
        AddScore(200);
        break;
    }
}

Similarly, SPR_84 is a variant of Clam Plant that is already handled by another case.

As this switch has no default case, any unhandled sprite_type passed to this function will be ignored, leaving the score unchanged.