Thank you so much for you feedback, I am aware of the couple small issues. If you dig a prize right as the timer ends, it softlocks the game. Something I wanted to fix but just didn't have the time. Once your level gets higher, it really does help bringing it larger hauls. Silver stuff definitely helps with that too.
And to answer the question, Is there actually a golden rule? The answer is..... Yes there is. Just incredibly rare, I came across it only twice during all my testing. It is a 1 in 500 chance of appearing, the depth ranges from 80 - 100, and is worth a whopping $500, thus beating the game immediately if found.