In practice the Caesar cipher offers almost no communication security. There are only 25 possible ways for you to encode your message, so even without the key it’s possible to exhaust decode the message by exhaustively checking all keys. This program has been set up to do just that with the “break” option. Just type in your message and let it try all the possibilities for you.

To increase security with your shift cipher you can advance the key after every letter, changing the key and making it much more difficult to break using an exhaustive method. You will need to communicate to the receiver of the message what the initial shift is (by the value of what A equals initially) and how much to advance the key by every letter. This can be done by simply sending them through separate channels the letter and number they’ll need. So if you received the key “G5″ you’d have all you needed to decode the following message:

Zsu gtka nj Qhkscgwo Zozaoip ds dd ayrzw vwzwqjpzx unlj wnva kebh yw ywxua ljuow re’ft emwwlfhl trkspzjh tj.

Caesar Cipher is written by Joe Larson.

So I found this program on allegro.cc, downloaded the source, and did some editing to get it to work with the newest version of allegro, but didn’t make enough changes to justify calling it my own and could never get a hold of the original author, so I posted the modified program in the forums, but never put it in the official collection of Cymon’s Games. Then I came back to it, made several significant changes, enough that I don’t feel bad posting it here.

As a pretty display this program could have been something fun just to watch, but there is a game to be played here. Click on the fireworks to detonate them. Detonate 3 in a row of the same color and you’ve made a chain. Your score is the number of chains you chain together. Break the chain and reset your score. The difficulty is designed to ramp up slowly with only 2 types of fireworks coming infrequently progressing to anything goes at a breakneck pace as your chain count increases. You should never be without the color you need to complete a chain.

If a firework falls to the bottom of the screen without being clicked you lose a life, all existing fireworks are cleared, and the pace of the fireworks is slowed back down, but you keep any existing chains so you can continue to rack up your score unless you break the chain. Post your best scores here.

Fireworks is by el Hamil with additional work by Joe Larson. Fireworks uses the allegro library.

After making the C conversion of Tim Hartnell’s Werewolves and Wanderer I received feedback that the game should highlight in color certain words to make scanning the screen for information easier. So I set about changing the input and output routines to go through curses as well as adding color information in the text.

The original will still be retained for academic purposes, but this is the version that will likely be used to develop future Interactive Fiction games, if future Interactive Fiction games are to be developed.

Werewolves and Wanderer was written by Joe Larson inspired and based on the BASIC game of the same name by Tim Hartnell as found in ‘Creating Adventure Games On Your Computer’ (c)1984.

Werewolves and Wanderer is an old-timey text-adventure in the vein of Zork or Adventure, but much smaller. I recommend playing it in full screen. Werewolves and Wanderer is modified from the game in Tim Hartnell’s book Creating Adventure Games On Your Computer. This particular version of the game tries to hide little from the player opting instead to show you all exits and available commands.

You can get help in the game by typing ‘help’. You can get a list of available commands by typing ‘help commands’. You can type ‘examine’ in certain rooms and you may find some insight into the strange world of Werewolves and Wanderer. It might help to play with a pencil and paper and map out the castle as you navigate it, keeping track of treasure you find and monsters to avoid. Many things in the game are random, but there are a few fixed items. Finding them will be key to reliably navigating the dangers of the ancient abandoned castle.

Reading the code to Werewolves and Wanderers could be an excellent tutor for writing your own text-adventures. Make your own map, creatures, items, and goals, change out the elements in Werewolves and Wanderer and you’ve got your own original adventure. In fact learning how to do this sort of game on the forums is how this game came about.

EDIT: June 26, 2010 – The game has been updated to fix some bugs in the high score table and play again function.

Werewolves and Wanderer was written by Joe Larson inspired and based on the BASIC game of the same name by Tim Hartnell as found in ‘Creating Adventure Games On Your Computer’ (c)1984.

Rover Warsis a competitive game for 3 players. At the main menu you can choose to let the computer control any of the opponents. Then just into the game. Absorb blobs smaller than you, avoid balls larger than you. The last of the 3 player blobs left is the winner. Rounds tend to be short, not lasting more than a minute. A good enhancement would be some sort of score table between games to keep track of who’s won more games and declare a winner after a number of wins.

Rover Warswas written by Joe Larson.

Just like Nim this is a solved game, if both players know what they’re doing the end of the game is determined from the first move. Unlike Nim the solution is simple enough for you to figure out in your head so there’s no need for a trainer. Play the computer on the hardest setting and see if you can’t devise the strategy yourself. Then play it on an easier setting and see if you can’t catch when it makes a mistake and turn things to your advantage.

Pick Up is written by Joe Larson inspired by 23 Matches by Bob Albrecht and Batnum by John Kemeny both found in ‘BASIC Computer Games’ edited by David H Ahl (c) 1978.

The oldest recorded example appears to be that given in Arithmetica of Nicomachus who died about the year 120. He tells you to think of any whole number between 1 and 100 and divide it successively by 2, 5, and 7 telling him the remainder in each case. On receiving this information he promptly discloses the number you thought of.

Can you discover a simple method of mentally performing this feat? If not, you can see how the ancient mathematician did it by looking at the source code.

Nicomachus was written by Joe Larson based on a BASIC program by David H Ahl as found in ‘BASIC Computer Games’ edited by David H Ahl (c) 1978.

This program attempts to replace all that tedium. Simply input the sizes of the respective armies and let the computer tell you the outcome. The results of combat are, just like in real life, sometimes surprising. And while a true Risk affectionado would never replace real dice with a computer program, if you can get two people who agree to let the computer settle their disputes this program could significantly cut down the length of combat in a game.

Risk Dice is by Joe Larson

Nim is a solved game, which is to say there has been discovered a mathematical formula that when followed guarantees the outcome within the first move or two. If one player knows how to play nim mathematically they are almost guaranteed a win against anyone who doesn’t know how to play nim, which makes playing against the computer not as much fun. On the other hand if you can learn how to play Nim mathematically…

This program, instead of merely playing a perfect game of Nim teaches you how to play a perfect game of Nim by showing you it’s mind set. The first thing you need to know about playing a perfect game of nim is the relationship between decimal numbers (like you’re used to counting in) and binary numbers. Once you know that you can use the binary representation of the number of sticks in each pile to develop a “nimber”. That nimber can then be used to plot your next move. Always try to leave your opponent with a nimber of zero until the end and you’ll be assured the win.

The one shortcoming with this trainer is if you miss it proceeds to school you through hard knocks. It would be better if it intentionally threw the game, but at the end of each round gave you a report card based on the number of rounds you gave it a nimber of zero, and offered other training modes that didn’t help you quite so much so that you can practice in a more “real” situation, without the hints. So that’s your homework. Rewrite this program to make it a better trainer.

Nim Trainer was written by Joe Larson

This game can be a practical example of algorithms vs heuristics. An algorithmic approach guarantees a solution in a fixed number of moves and the program could be modified to do the solution itself. A heuristic approach takes advantage of partial orderings already in the list at any moment. The number of moves it will take is less predictable with a heuristic approach. Programming the game to solve itself this way would require a fairly robust grasp of mathematical and logical thinking to pull off.

Reverse is written by Joseph Larson inspired by a BASIC program by Peter Sessions as found in ‘BASIC Computer Games’ edited by David H Ahl (c) 1978.