Invisible effect.
When a NES game want to temporary hide an on-screen object it often modify all colors of this object palette to the background one. The trick doesn't work really well with 3dSen because of depth, lighting and shadow are always still there. To regenerate this effect, you can link the target shape pattern with the following script:
function UpdateS()
local p = shape.Palette
local c1 = Palette.FrameColorIndex(p * 4)
local c2 = Palette.FrameColorIndex(p * 4 + 1)
local c3 = Palette.FrameColorIndex(p * 4 + 2)
local c4 = Palette.FrameColorIndex(p * 4 + 3)
shape.Enable = c1 ~= c2 or c2 ~= c3 or c3 ~= c4
end