It’s a shame all the creatures go by so quickly! The atmosphere was outstanding.
The idea is very effective for such a simple gesture (though the description confused me a bit… did you mean LMB instead of RMB or am I the one getting left and right mixed-up again?) – even so, it did not grab me completely. Maybe a more full version could fix that with a gradual ramp-up in speed.
It’s probably a bit childish of me to point out that if you need to explain your connection to the theme, you might not have adhered to said theme that well – but I will do it anyway.
Lastly, since you asked for my scores, in my two play-throughs I got 270 and 347 creatures saved respectively. It didn’t feel like that many even passed by!