Decisively simple and addictive game. Unlike other runners I've played so far, this one does actually have some strategic depth. The way this game makes you experience in-battle time is indicative. Some of the islands can be taken with lesser numbers but with more thought out, time and damage efficient abilities applications. Also this liberty has its limits it's nice to play a game that actually allows you some room for strategic thinking, while also staying true to its genre roots. By that I mean slow, but uniform and constant upgrade progress. Strategic thinking, however, is not only applicable to the battlefield space, as at some point I've discovered that troops positioning before the extraction have an effect on their survivability (especially archers). Landing preparation is a mini-game in itself, as it allows trying different approaches to the descent complication, and, therefore, different playing styles (troop-heavy, abilities-heavy or balanced).
I think the visual style, music and overall Viking theme applied very well to the gameplay style. On the one hand, economical system and overall story create a conflicting mix of profit and liberation and on the other - battle mechanics allows combination of daring boldness and strategic cunning. As good as this initial elements are, though, this game plays them overly cautious, allowing repeatability to slip in. With that said though, I've never beated an island in more than three attempts, and only on the higher levels.
With all that said, this game, as it is, does not go in depth to explore its own space. The backgrounds, as were already noted before me, are less then functional, having little to no gameplay significance whatsoever. This significantly reduces importance of player's visual awareness and reaction during the action. During the game (especially later stages) I was mostly looking on abilities icons, since it is vital to know when one of them was fully charged. Because of it the game does become quite repetitive and monotonous closer to the end. This problem became especially clear for me after rather disappointing boss battle, during which I had no options rather than sit and wait till one of the skills is recharged.
Overall, this game's mechanics and style have good potential, which would have been realized more fully if not for rather reserved approach to the game's visual space.