What Blocks In This Image Can Be Spawned On By Enemies?

[Warm Water]

Now, I've made a decent, unfinished build. However, a goblin army arrived. I assumed they literally could not bother me due to every single block having a wall I placed myself by or behind it, yet somehow they can still spawn on the clouds and on the house

The only blocks without background walls on them would be the dirt, and the house. So how do they manage to spawn on the clouds, which I had to manually place background walls behind the less combative reason of light shining through clouds extremely brightly in the day

another interesting thing is that if I stand on the floor, then only when this torch is offscreen:

Can enemies spawn on the left. But if I jump up a few planter boxes, or stand here exactly:

Can enemies spawn on the right.

Jumping above this cloud allows enemies to spawn on and in the house itself, along with on the left, as those blocks are offscreen. However, standing on the clouds do not allow any spawns

 

[9Craft 🌳]

that is confusing. were all the background walls in the house placed by you? naturally placed walls allows enemies to spawn
maybe place walls behind the clouds and dirt, that might help. but idk.

 

[Warm Water]

that is confusing. were all the background walls in the house placed by you? naturally placed walls allows enemies to spawn
maybe place walls behind the clouds and dirt, that might help. but idk.

every single wall was placed by me, and every cloud has a wall behind it placed by me earlier because otherwise it would be shining in the day

I don't think the dirt needs walls, as the goblins are spawning on the clouds

 

[9Craft 🌳]

very confusing...

 

[Warm Water]

very confusing...

indeed

 

[Golden Heretic Snakeboat]

the reason that enemies are still spawning even though you have background walls up is because when determining to spawn most enemies (enemies like harpies and wyverns are exempt from this), it game will start searching downwards for a valid block, which it is doing here during the goblin army.

the only way to stop this is to line the border of the background walling with solid blocks, or to extend the background walling upwards until the game can't find a valid space to make an attempt at spawning an enemy

 

[Kellam Yoshikage]

Enemies can spawn up to 47 blocks above the player, so one sure way to stop spawns would be to place walls all the way 47 blocks above where the player is standing; this would be less effective once you start moving higher up, though. A ceiling would be more effective, though I've still had odd cases of enemies spawning on player-placed walls during events and similar. Events also seem to remove the restriction worm enemies have about not spawning while the player stands in front of player-placed walls...