Night Elf: can now hide wisps behind the forest. This makes elf workers too safe.
Undead: wants critters like frogs for their creeping with skeleton rod.
Human and Orc: many creep camps only have heavy armor creeps. Adding some medium armor units helps them creeping.

Map size is good for 1v1. Lava areas and texturing are pretty nice.

looks good

Here's a small update:
v1.1
- Terrain and doodads improved after replacing from Lava Cracks tile with Rough Dirt (Barrens) tile.

It's a very cool idea for a map, but I think the chances of being pinned down by an opponent are very high because of the structure of the map

Review - Right Triangle Island
(Version January 3rd 2024)
Synopsis: Magma Marble is a melee map for two players featuring the Sunken Ruins tileset. The map's largest feature is a great wall that spans across the map, creating easily guardable chokepoints that must be crossed to access the enemy territory, enhancing the sieging aspect of Warcraft III.
Map Aesthetics: Visually the map is okay, though at times it looks empty and rather dull. The vibrant tileset choice helps to fight this but it still peaks through. Additional flavor is brought by the lava pools. I'd recommend placing pathing blockers or other obstacles on top of the wall edges to improve visual clarity on which areas can be accessed.
Map Layout: The map layout is interesting with the wall splitting the map in two. The existing pathways are sufficient, though there could be even a third one - for example near the red camps.
Neutral Objectives: The neutral objectives are adequate for a map this size. The red camps are too tough to be comfortable with - facing a Level 24 camp is hard as it is but in such a small two-player map with that weak of a drop? I would expect the camp to drop an Artifact. Another thing is the red camp's placement - at the corner of a wall, far away from bases, at the end of a dead-end corridor. It's a very unfeasible camp to take due to the investment and mispositioning required for taking it. The item drops (other than green camps) seem to be on the weak side. The expansion gold mine camps also have quite tough creeps guarding them - you might want to tone them down to allow faster expansion as it would support the layout of the map.
Map Gameplay: The gameplay properties look promising and could support a different style of melee. The narrow entry points that can be guarded are a cool mechanic and the secondary entrances are even guarded by creeps. Nice job. The current state of creep camps does not support a longer, slower game that is required for this layout to shine though: instead of slower fortify-and-siege gameplay, the players will opt to harass each other with quick strikes and the unusual layout never gets to do what it could.

Recommendations:
Fix the gaps between the trees.
Fix the item drops and creep camp strength to support the size and layout of the map.
Fix the Starting Locations to be equal distance away from the gold mines.