Remember the days in high school when the teacher would try to explain integrals to the class and every single person would be furiously pressing buttons on their calculator? Well, it's finally time to let the secret out - they weren't trying to solve any equations...they were trying to avoid hitting their own tail in Snake.

Graphing calculator games are one of the most overlooked influences on casual gaming today. For many, it was the only game experience they would be able to have until college. (I've got a friend whose parents wouldn't let him play any video games he didn't program himself for the calculator.) For others, it was a welcome distraction from chemistry, calculus and the cafeteria. Many of these games were simple ports of other classic games like Pac Man, Tetris and Super Mario Bros., but others were less mainstream games that were equal parts original, addictive and creative to the point that they got massive exposure and inspired other more mainstream games.

SNAKE

Snake was a game originally pre-loaded on Nokia mobile phones in 1998. While it found a small audience on phones, it didn't really become a talking point until someone had the bright idea of loading it to calculators. The game involved a snake on a playing field that the player had to direct to a pixel on the screen. Each time the snake ate a pixel its tail grew longer. Bump into the wall or your own tail and it's game over.

Snake lives today in flash form on the internet in many places. Casual gaming site Neopets adapted their own version of Snake called Meerca Chase while first-person shooter TimeSplitters 2 had an analog version of the game called Anaconda. It continues to be one of the more addictive free game experiences on flash sites everywhere.

BLOCK DUDE

Block Dude was an original game for the graphing calculator that involved a character that could move blocks on a 2D plane. He could only jump up one step at a time, forcing him to move blocks around the level to get from Point A to Point B. The programmers of this game put forth some incredibly challenging puzzles that would get you scratching your head in bewilderment before class was over. The number of blocks (and thus the difficulty of the puzzle) increased from level to level, making each puzzle more difficult than the last.

While Block Dude is one of the many calculator games that seems to have vanished to free Flash versions online, many of the key concepts in Block Dude, such as spatial recognition and resource use, can be found today in games like Portal, where the player must use a gun that shoots portals to manipulate space and get to the exit.

DRUG WARS

Before kids knew about Grand Theft Auto, there was Drug Wars for the calculator. A port of an old DOS game created by John E. Dell in 1984, the player took the role of a drug dealer in New York City. Traveling to the well-known locations of Manhattan, The Bronx, Coney Island and Brooklyn, the player buys and sells various illicit drugs with the eventual goal of being the richest drug dealer in town. Along the way, police try to stop you from selling drugs. In order to completely win, the player must have $50,000,000 when the game ends to achieve a score of 100/100. Drug Wars was the most complicated mainstream calculator game with a number of items and options akin to RPGs.

Drug Wars is easily the most popular calculator game available, spawning Dope Wars, a version available on browsers, iPhone, computer desktops, MySpace and Facebook but involves even more illicit activities and is much more reminiscent of modern-day Grand Theft Auto games. Dope Wars plays up the RPG elements of the original games, but still keeps the cornerstone gameplay of buying and selling drugs. This concept would be further realized in the Nintendo DS game Grand Theft Auto: Chinatown Wars.

Perhaps the biggest shame of the Drug Wars calculator craze is that it took students away from learning some of the core economic concepts of supply and demand in the classroom - a lesson vital to succeeding in the game. Then again, I'm not sure teachers would have wanted their wisdom to go toward their students selling drugs on a calculator.