Mind numbing and addictive
It's a computer game. One of many hundreds of "match three" type puzzle games, where you slide or shift symbols on a grid to form rows of three or more to make them disappear. Each time you make a cluster of symbols disappear you get points, and very often the colour of the grid will change. The game is won, either by collecting a pre-defined number of points, or by changing the background colour of the whole grid. Some of the older and well known games of this type are Bejeweled and Jewel Quest, which have been around for several years now.
The Big Kahuna Reef gameplay is the "switch two items to line up three or more" version, as opposed to other games where you slide whole rows of items along. The items are ocean related: nautilus, sea urchins, crabs, glowing fish skeletons, and old cannon balls to name a few.
When you clear a certain number of items with one move you get rewards, such as sticks of dynamite, bombs, and nuclear devices. They explode with impressive results as you switch them - or double click them - clearing up to half a grid at a time. This is typical for this type of game, and indeed most games: you get some power-ups of some kind, which help you get more points faster.
Big Kahuna Reef (2001), and the sequel, Big Kahuna Reef 2: Chain Reaction (2004), are very pretty to look at provided you like fish. The background behind the grids are beautifully rendered pictures or sea-scapes, with colourful fish swimming pleasantly around. In fact, every time you complete a stage you get more fish which you can add to the reef, thus populating your own Kahuna Reef.
The one thing, though, that I think sets Kahuna Reef a little apart from your run of the mill match games: it contains actual information.
Every time you unlock a fish you get a short, interesting factoid about this particular species. I never knew anything about the Blue Headed Wrasse, or the Parrot Fish, or the Bicolor Damselfish. Now I do. Not a lot, I admit, but enough to make it quite interesting every time a new fish gets unlocked. There are some 40 different fish and crustaceans plus one whale to unlock and read about. Even my all time favourite fish, the Sunfish, is there.
I always play this game in a timed mode, but there is a relaxed mode for those not wanting the stress of having to finish before the time runs out. I recently discovered that the music score - a fairly simple theme played over and over, just as is the case with most games of this type - is quite nice and soothing, especially heard through a good headset. Lots of nice bass, and the explosions sound very cool.
Developed by Reflexive
A very interesting article on the subject of this type of puzzle is found here, and the "match three puzzles" family tree can be seen here.