The game is mediocre at best. It works fine for the most part, but the game is very boring. Yes, it's a standard idle game, where you mostly just wait for things to happen, and you have to wait for what you want to happen. I suggest not spending any money on the game. This game is a fun distraction here and there, but honestly, there's nothing there to hold your attention for too long and is not worth investing anything into. However, the main thing that holds back this game in terms of it being fun is the currencies in the game. Gems are the standard "pay to win" currency used by paying real money and basically allow you to buy what you need to advance in the game. Nothing too bad here, and the gems work as most of these similar games have similar currencies. The amount you get in potions needs to be rebalanced. As some people have mentioned, you get to a point where you just never have enough potions and you end up sitting on upgrades for weeks because you don't have any potions, and by the time you get potions, you've moved on to another mine and end up spending them on something else. A few people in reviews have mentioned this, but I don't think it's as big a problem as people think. There is a simple way to fix this which I will mention later. Events serve little purpose other than temporary rewards that ultimately mean nothing. Sure you can try the events for things like gems, or potions, or chests/cards. But in the end, the events just don't amount to enough to warrant even attempting them. This is a problem many idle games have with timed events and this game is no different. Don't play the events. It's not worth the time. Invest your time into something more productive. Timed Idle game events are rarely ever good enough to sink time into especially when they only last a few days and you will lose your progress. The last currency has the biggest downside. And that is the gold. Gold serves almost no real purpose to finishing the game, and you can easily finish the game without getting a single piece of gold. There are only two things you can do with gold, and that is either buy goblins or upgrade shafts. Buying goblins means nothing because you get free goblins periodically, and you get them far more often than you would buy them (thus making buying them pretty much useless). And because getting gold means nothing, upgrading shafts really does nothing for you, and is just something to funnel your gold into since you have no other purpose for it. Now, two of the major problems with this game could be fixed with one simple change. And that change: remove potions and make gold the main currency other than gems (which would be used to either buy gold instead of potions, or used to forcibly upgrade mines like normal). That way, the problem with never having enough potions can be solved by using gold, and the gold gets a purpose that helps you complete the game. Otherwise, the gold serves no purpose, which means you don't even need the mines, which means you don't even need the cards or upgrades to the mines, which makes most of the game irrelevant. If the currency was re-balanced, the game would be far better off, and I think it would benefit the game. The currencies not being properly balanced and/or useful is what really holds this game back from being a better idle game.