Stomping while jumping

Verified against the spelunky.ai port v0.1.12 on 28 October 2026.

A stomp is meant to be a landing on a monster's head. But the touch code most monsters share doesn't ask whether the player is coming down: jumping counts as well as falling, as long as he's higher than the monster's middle. So jumping up into a monster from just below kills it as a stomp, and he bounces off it.

The player jumps up into a flying Bat from just below it and kills it, and bounces higher ^[1].

When a monster that inherits oEnemy's touch code touches the player within 12 pixels of its middle across, the first test is the stomp's. It accepts the player's JUMPING state (15) as well as FALLING (16), and only asks that his y be above the monster's y+8:

else if (not other.dead and (other.state == 15 or other.state == 16) and other.y < y+8 and not other.swimming)
{
    other.yVel = -6 - 0.2 * other.yVel;
    if (global.hasSpikeShoes) { hp -= (3 * (floor(other.fallTimer/16)+1)); scrCreateBlood(other.x, other.y+8, 1); }
    else hp -= (1 * (floor(other.fallTimer/16)+1));
    other.fallTimer = 0;
    playSound(global.sndHit);

A player rising into a monster from just below is jumping, so it's a stomp: the monster loses a hit point (three with Spike Shoes), and the player is bounced up, yVel -6 less a fifth of what it was (after his own step's gravity, which comes first). A Bat has 1 hit point, and its step kills it once they're gone ^{[2] [3]}.

Jump up into a Bat, or a Spider dropping from the ceiling, from just below, so that the player's middle is above the monster's when they touch. It happens in normal play. The replay of the clip jumps on frame 1073 and, still rising, hits a Bat: on 1076 the stomp's bounce, after his step's gravity, takes the player's yVel from -3.4 to -5.4, and the Bat dies on 1077 ^[4].

The spelunky.ai port reproduces it exactly: it's in docs/quirks.md's list of the 1.1 source's bugs ^[3], and the oracle's fingerprint of the replay pins the jump, the bounce and the kill. No option turns it off.