It was not written in the rules in detail, so I will talk about it here. First of all, the timer starts measuring the moment it gets dark after you select a level in the level selection screen. So why is that the starting point? It is mainly for the purpose of aligning the starting points. And although I haven't tested it, the speed at which the darkness is lifted may change when restarting.

For these reasons, it is allowed to use restart in any% of IL, but the total time will be slower. Of course you can use minimum.