I think my current world design fits the challenges pretty well, but not perfectly. The hill is too steep, oops, and the gap between the spawn point and mainland in the river is too short, whoops. I probably should change those attributes, but time is not on my side and the current layout serves its purpose well enough. I think the challenges should match the world through model choice and theming: emptiness and vaguely anachronistic structuring. They also should be simple and short, to match the limited layout and options for complexity.