At first it looks like Mystery Gold is a Dig Dug clone, but there's not too much similar besides a surface-level glance of the environment. Now that I think about it, almost certainly you're in a mine, not a garden, and you have to gather gold to progress levels. You shoot baddies instead of pump them up and cause them to explode. And there are water sources that can start to fill up the maze you've dug (although I haven't captured a photo of that particular situation; as there is no pause it is quite hard to take photos of Pyuta games!).

I got a boxed version of this one!