Creeper able to pass through walls?

[Awesomeclaw]

I've noticed this also in older CW games - in certain circumstances (especially with unusually high concentrations of creeper, e.g. >1000) the creeper can pass through solid walls. I'm currently playing Ephemeral, and as soon as I opened the area with the pod, creeper started phasing up through the solid wall and into the central channel. Not really a huge issue but seems very weird?

[illegal legos]

In older games, creeper could be dense enough to overflow the hard height limit on terrain.

In Ephemeral, opening that chamber requires you to lower the lava, giving it room to flow around and trap some creeper inside it. Once the creeper is in any terrain it will flow out until it reaches air.

[Happy Monkey]

If creeper appears in an area with no access to open space, or the open space that creeper is in is filled in, the creeper will flow up over land until it finds a place to appear.

[Gra̶bz]

It's possible opening the area caused some sand to fall inside the cavern. When you drop sand that blocks creeper into creeper, you cause some amount of creeper to become [inside terrain]. So that creeper isn't stuck in walls, the game's behavior in those situations is to apply a field of a certain strength to creeper to push it out. In the case of most terrain types, this behavior is to push creeper upward. There are some exceptions, e.g. acid pushes creeper down instead, but the behavior you will see the most if creeper flowing upwards until it can rest in the first empty tile it encounters.