Classic Computer Magazine Archive START VOL. 3 NO. 6 / JANUARY 1989


by Thomas Bürglin

In this ST version of a classic video game, you're Spencer the Snake and your goal is to devour apple after apple fast enough to beat the clock. So whether you have a color or monochrome monitor, warm up your fingers and cancel your plans for tonight. Spencer needs your help! (Ophidiophobes are strongly urged to steer clear.)

Slimy snakes slither slyly-con you? File SLITHER.ARC on your START disk.

Slither is a snaky way to test your hand/eye coordination. In a series of increasingly difficult levels you must make Spencer the Snake swallow a half-bushel (or so) of apples. Eat all the apples and you advance to the next level. But watch out! Spencer's metabolism has been warped by DDT and the longer he slithers, the longer he grows. Written in Personal Pascal 1.1, Slither runs in both low and high resolutions.

To play Slither, copy the files SLITHER.ARC and ARCX.TTP onto a blank, formatted disk and un-ARC the file following the Disk Instructions elsewhere in this issue. Double-click on SLITHER.PRG and a few seconds later the title screen will appear

Playing Slither
Press the Space Bar to begin the game. Spencer, your friendly serpent, will slither out from the bottom of the play field. A little red apple, Spencers favorite (and only) snack, will appear. Use the left and right arrow keys to steer Spencer to the apple. When he swallows it, another one will appear someplace else on the field. The goal is to help Spencer eat all of the apples in a level.

If Spencer rams into a wall or barrier or bites himself, he has to repeat that level. But if he eats all of the apples in a level, he can escape to the next level through an opening that appears at the top of the play field. And the next level is (naturally) even harder.

On the left side of the screen, you'll see the number of apples Spencer must eat in that level and on the right side of the screen you'll see the timer bar. If Spencer doesn't eat an apple before the timer runs out, three extra apples will appear. Sound like heaven to a hungry snake? Well, Spencer grows so fast that if he has to eat too many apples, sometimes he can't get his tail out of the way. And for a snake, that's a tragedy!

Through Spencer's Eyes
The snake controls work from Spencer's point of view, just put yourself in Spencer's place: to turn left, press the left arrow key. To turn right, press the right arrow key. This may seem confusing at first, so it's wise to use the Practice mode (see below) until you get the hang of it. In the Game mode, Spencer only has three lives, but in Practice mode Spencer can be reborn any number of times.

If Spencer is a bit too fast for you, press the 2 key at the title screen to bring Spencer Senior into the fray. He's a little older and a little slower, perfect for magazine editors (and others) with slow reflexes. You can pause the game with the right Shift key; press any other key to resume play. The Alternate key takes you back to the title screen. Finally, press the Escape key at the title screen to quit Slither completely.

Spencer Scores Again!
Slither has 30 levels and each apple is worth 10 points times the level's number (Level Three's apples are each worth 30 points and Level Five's are worth 50 and so on.) Every time you eat an apple Spencer will grow a little longer and become a little faster, making it more difficult to maneuver. If you're able to complete a level without killing Spencer, you'll be awarded bonus points.

Practice, Practice, Practice
Want to practice a little? Press the 1 key at the title screen. This will take you into the Practice mode. Although you can kill Spencer, he can never be sent permanently to Snake Heaven. And, although Slither won't increase the total number of apples Spencer has to eat in a level, you also don't score.

Creating Levels
If you become bored because you can reach Level 30 in your sleep, wake up! You can load new Slither fields by pressing the 5 key at the title screen. Load the sample file FIELDS.TXT to change the playfields in levels two through five. To restore the original play fields, press the 6 key at the title screen.

Slither is a lot of fun, but harder than it looks. . . until you
get to one of the higher levels, like this one, where it is as
hard as it looks.

You can also create a "fields" file with any word processor that can save a file in ASCII format. The first few lines of FIELDS.TXT are shown here:

2 3
128    0    0    0    1
128    0    0    0    1
128    0    0    0    1
128    0    0    0    1
128  255    0  255    1

The first number on the first line tells Slither the first level to replace and the second number is the number of levels in the file-the total number of Slither levels cannot exceed thirty. Lines 3 through 41 define the first new play field. There are five numbers on each line separated by spaces. Immediately following, with no empty line inbetween, are the 38 lines that define the next play field, and so on.

Each play field is composed of 38 rows of 38 units per row (40-by-40, including the walls). The third line of the file is the top row inside the play field and the 41st line is the bottom row.

The play field map is stored as five bytes (40 bits) per line, The first decimal number in a line must be equal to or larger than 128 (10000000 binary), because the hit furthest to the left in the eight-place number defines the left wall. Similarly, the last decimal number in a line must be odd, since the rightmost bit defines the right wall.

To define a play field, draw it as a 40-by-40 unit grid on a sheet of graph paper Place a 1 in every unit where you want a wall or barrier to appear and a 0 into each open space unit, then divide the grid vertically into five columns of eight units. Each row on the grid will then have five groups of eight binary digits. Convert each group of eight units into the equivalent decimal number; these are the decimal numbers for your text file. If you're unfamiliar with binary numbers, study the sample file to see the effects of different numbers.

(Editor's Note: If you don't want to go through this process, wait a bit-we have a Slither Construction Set in the works for a future issue of START.)

When you take on the Slither challenge, you're taking on a game that requires skill and patience. You'll probably come across some levels that you'll think impossible to get through (some people think Level One is impossible). My only advice is to keep practicing, and practicing, and practicing.

Oh, yes, ophidiophobes are those with an unreasonable fear of snakes.

Thomas R. Bürglin is a research scientist in molecular biology. He is in the United States on a two-year sabbatical from Switzerland to finish his Ph.D.