This is one of those nice cartoons that just kind of fell through the cracks. Made by a regional studio in the Ural mountains, lacking even an entry on animator.ru... it is a good geometry introduction for kids, and I think the character design and animation are very polished. Though the ending promises a continuation, it does not seem like the director ever made one. Someone else at the studio directed a 1976 sequel, but it is not as good.
It was unusually difficult to find who the director was - it seems that the Sverdlovsk Film Studio in this period often just listed everyone as "film crew" in the credits without differentiating their roles. Some film databases list it as being directed by Nina Pavlovskaya... but she only started directing in 1976 (that aforementioned "sequel" was her first film...), and was not even in the credits here, so I figured it could not have been her. Eventually, I found an off-hand mention in an article on the studio's website confirming that it was directed by Galina Turgeneva. She began to direct films at the Sverdlovsk Film Studio in 1957, but this apparently included educational/documentary films as well, so I have no idea when she directed her first fully-animated film. Maybe this was it. She has been described as "the founder of Sverdlovsk animation", and she set up the studio's (non-educational) animation division in 1973, just after finishing this film.
The translation presented no special difficulties, although I will note that the Russian word for "angle" and "corner" is the same, so that part of the lesson is just a little more obvious.