The Yeti King's harmless touch in custom levels

Verified against the spelunky.ai port v0.1.11 on 28 October 2026.

The game keeps custom levels out of its statistics with a check, "is this one of the game's own levels?", put around each tally. Around the Yeti King's touch, it went around the damage too, so in a custom level the touch takes nothing. Around its kill, it was left out, so that kill is tallied even there.

In a custom level the player walks into the Yeti King twice: it knocks him back and he blinks, but he keeps all four hearts. A bomb then kills it, and the kill still goes into the lifetime tally ^[1].

The Yeti King's touch knocks the player back and makes him invincible for 30 steps, then takes its 2 hearts only on one of the game's own levels:

else if (other.invincible == 0)
{
    other.blink = 30
    other.invincible = 30
    if (other.y < y)
        other.yVel = -6
    if (other.x < x)
        other.xVel = -6
    else
        other.xVel = 6
    
    if (global.plife > 0 and isRealLevel())
    {
        global.plife -= 2;
        if (global.plife <= 0) global.enemyDeaths[14] += 1;
    }

isRealLevel is, as its own comment has it, "Only used for stat-checking atm.": it's true in the game's level rooms and Olmec's ^[2]. Every other monster's touch takes its hearts first and checks it only for the tally, as a Yeti's does ^[3]. The Yeti King's kill is the other way round: its step adds it to enemyKills[14], the lifetime tally of the statistics' YETI KING row, without isRealLevel() ^[4]. Every other monster's kill but Olmec's, which only his lair has, skips that tally outside the game's own levels ^[5].

Make a custom level with the level editor's Y, and walk into it: it knocks the player back, and he keeps his hearts. The level editor's test does the same. The replay of the clip's staged scene, on a custom level, walks into the Yeti King twice, and the player keeps his 4 hearts; a bomb kills it, and enemyKills[14] becomes 1 ^[6]. On a real level, in a Yeti lair, the same touch takes him from 4 hearts to 2 ^[7].

The spelunky.ai port reproduces it exactly: it's in docs/quirks.md's list of the 1.1 source's bugs ^[5], and the oracle's fingerprint of the replay pins the player's hearts and the tally. No option turns it off.