This was a damn good game loop. Simple but immensely satisfying. You start as a chump, barely mining a few blocks before time was out. It was during this stage I discovered a diamond before I had time to mine it and it sparked a fire in me. By the end I was carving my way through the map, cutting diamonds like butter, optimising my bomb usage and ultimately wrecking shop in this pixel underworld. That's my one gripe. I agree with Squishy Turtle Games, in that the portals feel like an end to the fun loop you've built. But an immensely fun game and you should be proud, my first jam game sucked big time and barely worked, xD
Keep up the good work, you've got a solid core here!