I actually did manage to beat the game on my 6th try! The first 3–4 times, I didn’t realize I had to press Space to counter (turn around), so I just ended up staring helplessly while they attacked. Once I figured that out (by accident), it became much easier to get through.
For the instructions part, something like “Press Space when they get close” would help. Once I understood it, I did feel like a little more tension or a second threat in the background could take it further.