"Barbarians left" counter is inaccurate when investor is almost out of money
Normally there are 60 enemies per round. If the investor is close to being broke and a new wave starts, he logically can't spawn this many enemies.
This could be fixed by not stating how many enemies there are remaining for this round, but by giving the investor a budget for every round. The UI then shows how much of this budget has already been spent. The investor can overdraw his budget for exactly one enemy in each round and take the additional money out of his total funds. This ensures that the game can end if the investor is very close to being broke, but has more than 0$, but too little to buy at least one enemy.