A Sound of Thunder is not a racing game. It's an action game based on a sci-fi movie which was, in turn, based on a sci-fi short story by Ray Bradbury. The movie has been held up for a summer release but the game doesn't have time to sit around and wait. In keeping with the slogan of the title, Time is not on your side.

In the future, time travel has been perfected. Time Safari Inc. offers dinosaur hunting expeditions to the past where adventurers can track prehistoric monsters. To take part in the adventure there are three rules that must be followed: You can't change anything; you can't leave anything behind, and you can't bring anything back. In one fateful incident, a butterfly is accidentally killed which changes the course of evolution as we know it. As the time line catches up with present day an assortment of mutated creatures begin to appear. These creatures are the result of a natural selection process that is different than the one we evolved from one. To correct this situation a group is assembled to go back and figure out what went wrong.

Travis Ryer is the playable character. To save mankind he must kill the present day mutated threats, solve various puzzles and return to the past to fix the problem. The creatures are imaginatively rendered and stimulate your imagination to imagine "what if?"

To eliminate these creatures you will have various weapons at hand which include rifles, a grenade launcher and a grenade that stops time. A lock-on targeting system ensures that you will be able to negotiate the top down, 3D perspective favored to view the environment. Aiming has been simplified. It doesn't take much skill to take out the threats which in some cases is a good thing since some of these beasts hunt in packs and will surround you.

Time is of the essence and it's a commodity that you don't have much of. The environment literally changes around you as time waves reach present day. During the puzzle phases you will have to move boxes around to access areas safely and throw switches. As the time waves change the environment, certain paths and areas will change causing you to adapt your strategy to the new environment. It's an interesting concept that works and really forces you to panic.

The core of the gameplay tends to get a little repetitive but there are enough diversions to keep it from getting boring. One such diversion is the use of vehicles. It's not an amazing addition and the game could have easily done without it since the engine is not designed for it. The vehicle pauses for a micro-moment every 10 seconds or so as it leaves one area and enters another. The screen doesn't scroll smoothly; it sees each area as a different room and tries to link them together. The result is very choppy and annoying. It's a good thing this doesn't appear in every level.

You can feed a group of four hungry gamers off of only one cartridge. A four-player Deathmatch is available for only the price of a handful of Link cables. It's a really good mode with smooth moving sprites and an environment that has just the right amount of obstacles and open area to see your opponents. The area is somewhat confining but it does the job. There's even a co-op mode in which one player can drive the vehicle and the other can shoot at the creatures. It's not nearly as good as the four-player mode thanks to the stop-and-go motion of the vehicle.

The characters are well rendered. They animate very smoothly in real time. There's not much background music but when the action starts it kicks in and really helps to get the blood pumping.

This is one of the few times that a GBA game has actually piqued my interest in seeing the movie that it was based on.