by Jacob S.
"I thought of valleys by the two spikes on my tessellation.
I added green in the middle and it started to look like a valley."
If we call this a tessellation, then it is Heesch Type TTTT
With the internal decoration looking like a green sky or a field of grass, this is symmetry art but not an Escher-style tessellation. That's because the sky is formless filler-- and the grass might be a sign of an overlap. Is there some field hidden behind the mountains? We don't know, because fields are formless. So... since a tessellation is "a repeating tile pattern that fills a plane without gaps or overlaps", we can call this a tessellation ONLY if it's not colored in with sky or grassy fields. Sky is gaps; grassy fields may be gaps or overlaps.