Sometimes, you have to go with what works. It's no secret that some mechanics are tried-and-true, and will allow you to please gamers while adding in your own twists. Sometimes, though, it's evident when a game borrows a bit too much and doesn't give enough back.
Happy Vikings mixes gameplay from a number of different classic puzzle titles, including a lifting-and-matching mechanic from an NES game called Wario's Woods. Instead of just flipping tiles with a cursor, you actually have a sprite in the puzzle area which you can use to manipulate tiles. This is the titular "happy Viking." Our Viking (let's call him "Olaf") can lift and push treasure, booze, and food to form shapes beginning with three tiles.
After matching tiles, they presumably get packed away into the Viking ship, ready to be brought back to their home village. Tiles appear by way of catapult, and are finite: the number at the top of the screen isn't a timer, but an indication of how many treasures remain to be flung onto your ship.
The ability to move tiles around without the requirement for them to match to anything makes for a great combo-building experience; it's what keeps games like Bejewelled from becoming a tactical puzzler by relying on blind luck. Olaf's a pretty strong guy, and can push tiles up to two blocks high. Also, he can pick up blocks and push them while he's got one on his back. He clearly does his squats.
Controls are handled via on-screen buttons which do the job well. You can move left and right, (double) jump and lift. Tiles are affected by gravity, which means that you're encouraged to make chains and combos; this gets taken a step further by the introduction of runes, which when arranged in a way to spell out words (like "Odin" or "Thor") gives Olaf different bonuses on the field.
The combo system works really well, and is very satisfying to complete. The fact that tiles have their own distinct colors make it easy to differentiate on the fly, especially when you've got other things to be worrying about.
What annoys me about Happy Vikings, however, is how little original product there is, here: you've got a naming scheme, scoring and level system taken from Rovio ([Adjective] [Noun], three stars and the episode-style menu, respectively), combo mechanic from Tetris Attack and the previously-mentioned Wario's Woods gameplay. It's essentially a Frankenstein of different games with a new coat of paint on it.
This isn't to say it doesn't do the appropriated mechanics justice, though; the game plays really well for something that relies on touch screen controls. The graphics are friendly, sounds appropriate, and the rune system is the touch of originality that it needed to keep from being a complete rip-off. At roughly $1.40, this game's a worthwhile purchase for any puzzle fan on the Android.