This is a demo of the very beautiful Trine, a platform adventure, with a mixture of physics based puzzles and hack-and-slashing.
The story is excellently narrated, and the introduction to the fairy tale like story is very well done. It's a 2D platform game, though the graphics are rendered in 3D. You have three characters, a thief, a wizard and a knight. The thief has a grappling hook, useful for swinging over chasms, the wizard can levitate objects, useful for many of the puzzles, and the knight is a big brute who's handy with his sword.
Switching between these three as you go along, you'll meet the army of the undead, and lots of treacherous scenery. There are regular checkpoints, and the only problem we saw was that sometimes you need on of the three protagonists, but can't use them as they are dead! Nevertheless, it's a really enjoyable game, with a gentle humor and a nice balance of gameplay from the three different characters.
The demo is well worth downloading, as it's quite an enchanting game. There are a good variety of setups available, which is good, as to take full advantage of the lovely visuals, you'll need a powerful system.
Trine is an atmospheric, and beautifully executed platform game, which deserves great success.