A technical marvel of the time. Some of the effects hold up better than others. There's a philosophical message at the end but it feels hindered by the knowledge and technology of the time. Given the current advancements in sub-atomic physics, I feel like the ideas brought about in the end would have been more fleshed out if the film was made today.
Also, the overreliance on the score is something that really bugs me about old films. Especially thrillers like this.