This was great, the mechanic was a great use of the limitation, although I did find just trying to get as high as possible then double jumping felt like an optimal strategy most of the time. I think the additional hazards you've mentioned in other comments sound great, they'd add another layer of strategy that would encourage a more considered approach, but still very much enjoyed myself with this.
Also really like the tension from the time limit - didn't notice the darkness approaching at first, but panicked once I did!