When facing a difficult challenge, use the "rewind" button as needed to test different strategies until finding one that works. When developing a strategy, try to determine the easiest way to win, either by killing all the enemy troops or destroying the artifact. Kill enemies one at a time, starting with the most dangerous one, unless you really have a very powerful area of effect unit or power-up. Because your enemy also only has five moves, they will rarely use more troops than one. Use the troops that you already have on the battlefield and wait for the best time to use cards. Protect your best troops by sacrificing one of your other units in order to keep the strongest ones alive. Move to the most useful power-ups if it is to your advantage. For example, do not approach the purple power-up unless you will be attacking the artifact.