Definitely nailed the essential to gameplay part. No way you could brute force it with the audio off.
The under the desk part through me off a little. I thought I could play with keyboard OR mouse. Took me a while to check my mouse. Would like to see a little more description of that, either via a post it note or in the game's description.
But the audio is the focus, and morse code certainly fits the bill on that. Nice job.