Though it's quite a pity this isn't the full game with all its additions,it is still enjoyable with its simple and yet quite engaging game concept that gives players enough to explore.The hidden coins gives the game a 'Easter egg hunt' kind of feel too and also a good reason to explore the underground.Maybe the coins could be used to buy stuff at a shop set up at some areas(who would have thought of doing that in real life?) like a diving suit to increase movement speed underwater(don't know if other players know about this,but pressing down and clicking the mouse would make the character go underwater slowly)and a pickaxe to smash rocks to reveal more hidden treasures besides coins.It would be also quite cool to find other types of characters like other people(miners with stories to tell) and animals(bats flapping around and dropping dung).The grappling hook is really useful in reaching those high areas but it can be quite hard to for the character to actually go there as he will become a swinging pendulum because the grappling hook will not pull him up,maybe pressing 'W' or spacebar could help fix this.Overall,this game is engaging enough to kill some time with it's 'free to explore' concept,so great work and keep it up!Oh and congratulations on winning first place!