That's a bit unfair! That's doctorate maths isn't it? Shooting a rocket between two objects one orbiting the other rapidly and taking into account their gravitational pull (and the sun's)..... Easy peasy Einstein.
I heard they did the calculations for the project with 1MB of computer power. The rest was brain power. Astonishing. There's a great pair of films about the space race called The Right Stuff based on a book by Tom Wolfe. The progress they made over a decade makes me think they did land on the...