The reasons I believe that it's a bug:

- The behavior is different from static tints defined in the prototype (the right circle):
more_tints.png

- The dark square around is smaller than the original image. Here's the same, but with normal blending mode for comparison:
blend_normal.png ...

Example entity:

--- @type data.SimpleEntityWithOwnerPrototype
local static_test = {
type = "simple-entity-with-owner",
name = "picture_test",
collision_box = { { -0.9, -0.9 }, { 0.9, 0.9 } },
selection_box = { { -1, -1 }, { 1, 1 } },
picture =
{
layers = {
{
filename = "__Test__/sprites ...

Demonstration of the problem: animation_sheets.mp4
Two similarly defined entities. Both use main animation with frame_count=32 , and an animation with frame_count=1 repeat_count=32 for the shadow.
The left one has its animation defined as animation with two layers . The right one uses sheets ...

If an entity has a layer with draw_as_light, and a regular layer on top, it renders differently based on whether space age mod is enabled or not:
- Without space age, the light from the lower layers is illuminating the top one: vanilla.png
- With space age enabled, the light from the lower layers ...

Steps to reproduce:
- Disable all mods, including the ones enabled in the save (space age and dependencies)
- Load the save.
- Observe the crash

Scenario:
- Create a tile with concrete (minable tile) over landfill (foundation tile) over water (non-minable tile).
- Use LuaSurface::set_tiles to set the tile to landfill.

Expected behavior:
- Tile now just have a landfill (as tile) over the water (as hidden_tile).

Actual behavior:
- Tile now ...

Documentation says that this method returns array[LuaTile].
Testing in game suggests that the result is actually array[LuaEntity], specifically ghost entities.