insufficient gold, troops lost... Why not just stop me from buying more troops? this is insta death for just not wanting to watch the stupid numbers the whole game.
This game is so buggy and laggy. Add to that the fact that there's no way to recover HP in towns so you're stuck just going the same route over and over until you get a lucky go when you're under 10hp
The secret is wealth towers. in the last few levels, make 5-6 wealth towers and then upgrade them to money steal when you have 5-6 other pure level 6 towers. I also like to use 2 confuse towers early on that get upgraded to teleport. place these in the prime location where you get 2 chances to teleport a monster.