After a round, when the original leader rolls to jump start the sun, it says: "Four or lower and the sun remains dark."
Is it intended that if they arrive at the end with only the d4, they have no chance of winning? If so, it might be better to discard the d4 entirely and make the d6 the lowest die. I feel the most exciting part of the game would be when you only have the last die and are trying to get to the end, a thrill following every roll. The way it is now, even if you have the last die, there's no reason to get to the end, as you lost anyway. At least, that's how I understand the current rules.
That one thing aside, the game looks great! Fun and simple. Good job!