Still easy.

The major twist of this test chamber is that there's an extra room before the one with regular flinging in it.

I have good eyesight, but the contrast on my computer screen is perhaps higher than usual and I can only see when the mapper has added proper lighting. Before deciding whether it is my fault or yours, ask yourself whether you paid attention to lighting or not. Different computer systems give different results; the only way to be sure that players can see in your map is to be diligent about lighting. I hope this is helpful. I did not vote thumbs up or down.

Wait, you have good eyesight like me, right?

I enjoyed the start of this map, especially the first move, but quite soon I found myself in complete darkness and unable to continue. I think you have forgotten to add lighting so that the player can see around himself.