Enjoyment: As you say, buggy, but I can see it being very satisfying with a bit more polish.
Concept: It's solid! Not particularly novel, but a good core mechanic nonetheless.
Presentation: I like the colour choice. The "don't let them get here" sign was also good, as it made it very clear what the goal was. Unfortunately, the frog's tongue kept glitching out of his head, which made it very difficult to catch anything.
Use of the Limitation: I reckon score attack was a good way to approach this limitation.