Sadly prone to crashes
(I'm giving this three stars because if you're happy to only play up to level 6.4, it's still a pretty neat game concept; the crashes don't render it unplayable as such.)
Well, yes. Level 6.4, where you need to clear everything and ask Boreas for help three times, and every single time bar one the game locked up, grabbed 100.2% of processor power on my Macbook, and stayed there. Bar once, when I wanted to document this crash again (a year after first reporting it) and much to my suprise, was transported to the next level.
Imagine my annoyance when after finishing I started playing the bonus level and the game crashed with a failed assertion every single time I tried to play the first bonus level. Every. Single. Time.
There's much to like about this game - some of the graphics are a bit twee, but there's a storyline and varied gameplay and you can make some decisions about which buildings to erect (though they seem mainly cosmetic); tiles, boards and gameplay are well-designed (a couple of levels are a bit tedious, but this clearly has been playtested and is well balanced) - but with persistent, repeatable crashes on more than one OS I hesitated about giving it even three stars.