This was a great temporary solution, because it disgusted me enough to inspire me to work quickly on a permanent design.
Special challenges of designing this shade involved allowing space for the projecting hinges and handles of the window, and for the inswinging casement window to open completely. These challenges were of course in addition to the ever-present one of keeping to the themes of the whole house - authenticity, natural materials, and honest detailing.
I sketched a single panel design that would slide up, another version that would slide to the side, and a single swinging panel. But I finally decided on double swinging shutters, where each leaf would swing open all the way and lay flat against the wall. At night with the light on in the bathroom, the shutters look solid:
But I built the infill panels with thin balsa wood that is translucent, so they glow during the day:
Here are the shutters partially open:
And then with the window opened all the way, the left shutter flat against the wall (made possible by spacing the hinges 3/4 of an inch from the wall surface):
Both shutters opened completely:
From outside at night, with the shutters closed and the lights on in the bathroom, the effect is similar to that inside during the day - the balsa wood panels glow (a much better image than me in the shower):