The idea is to complete the map with as much gold and experience you can get by defeating all the horde of enemies that will spawn. Each Map will have 3 levels of difficult. Completing in higher difficult will ensure you more gold per mob and experience. Also you earn a bonus at the end which will consider the time you spent and the mobs you killed.
The goal in the game is to unlock all the characters by completing the maps and farming gold and experience. To buy a Champion (I still need to think the name) will cost you experience and gold, but will only spend the gold.
There is a small chance to drop x20 gold and a token to unlock some of the champions that you don't have. If you drop a character token that you already have, you can convert it into gold.
Each Champion have a normal attack which you can use all the time. Also they have a normal skill and the ultimate. Both of them with cooldowns