Been playing this game last summer, when I was stuck.
And I discovered it again few days ago.
You have a map and a route. At the end of the route there is your base you have to defend against the monsters coming in waves out of a den at the beginning of a route. The way how you defeat them, is by building towers, to which you place gems. You can combine the gems in order to create higher level gem and make the most powerful combination gem to defeat them all monsters.
Now I just can't get myself over the first "epic" level and "epic boss". I know that the last time it also took me quite some time to pass that, but I made it. Ha ha, summer procrastination, here we go!
Only bad thing is that it's an online game and I can't download it and play it when I'm in Slovakia next week, where I have no internet access. Oh boo.