Absolutely loved this one, totally goofy is some aspects but the set pieces are awesome and it’s incredibly enjoyable. It felt like a colorized episode of The Twilight Zone with much bolder production.
With all that being said, there’s a dated kind of inevitable cheesiness to it so I think it’s impossible to call it scary or even tense. Science fiction from that general part of the century is obviously crafting the “science” part around total unknowns and bullshit.
I respect Bava for this one and I enjoyed it, however, I don’t expect that feeling to be universal.