Good, but some matchups are extremely annoying. Try mid- to late-game Poison Water vs Burning Hill. As PW, in order to avoid being killed by BH's huge combined attacks once they hit that special level, you have to alternately spam Poisonous Wave and Paralyze (and the computer will alternate between trying Combined Attack and Remove Effect), which will slowly drain your mana and their health until one runs out first, which can take even 15 turns of back and forth.
Tip: the more mana you have, the slower it increases. So a spell that costs 500 is going to take significantly longer than twice as much time to cast than a spell that costs 250.
Very good game, but some of the bosses (Drone Mothership, Living Heart) have huge blind spots in their shooting patterns where you can park your ship and just wait until it kills the boss.