Snow, a Perspective on Sheep Herding

by Chris Nelson

March 2, 2010


Snow is a sheep-herding game. The goal is to guide a herd of sheep safely to their grazing patch. You are hampered by the raging snowstorm going on around you. If a sheep enters snow, it instantly becomes lost. You must get a certain percentage of the sheep through the storm and to the grazing plot.

Basic Mechanics

The player’s avatar (a shepherd dog) must entice the sheep to travel in certain directions by moving opposite the sheep and ‘bark’ing. The sheep will then move in the opposite direction as the avatar.

Moving the Avatar

To move the avatar, the user types in a series of buttons to move in a certain direction. If the user presses the keys to move, eg, both left and up, the avatar will move at 1/(v2) base speed in the diagonal. At the developer's option, the avatar might also follow the relative direction of the mouse pointer.

Moving at the Sheep

In order to entice the sheep to move, the avatar must ‘bark’ at them. The user accomplishes this by pressing a specific button, either on the keyboard or on the mouse, if the mouse movement option is being used. After the ‘bark’ has been completed, any sheep adjacent to the avatar move in the opposite direction as the avatar to the sheep.

Sheep-Snow Collisions

If, in their motion, any sheep enter the same area as a snowstorm, the sheep becomes lost in the snow. In this case, the sheep disappear from the screen and the sheep lost count increases. If the sheep do not encounter snow, they do not become lost.

Sheep-Grazing Collisions

If the sheep manage to make it to the grazing patch without previously entering the same space as a snowstorm, then they disappear from the screen—the sheep lost count does not, however, increase. This allows for multiple sheep to make it to the grazing area.

Round End Condition/Results

The round ends when all sheep have disappeared from the screen. The user is displayed the sheep lost count. If the ratio of sheep not lost to sheep lost is greater than 0.8, the user is then brought into another round—otherwise the user is displayed a game over screen and given the opportunity to continue the game from round 1.

Initial Setup of Rounds

At the beginning of each round, a number of sheep and snowstorms are created as equal to the number of the round. Round one, for example, has one sheep and one snowstorm. The sheep are arrayed in a pattern around the avatar on the left side of the screen, and the snowstorms are randomly arrayed around the screen—the do not, however, overlap the avatar or any sheep. A grazing patch is placed on the right edge of the screen, at a random height value.

Game End Condition

The game is won if, at the start of the next round, there would be no available places to place the final sheep; if the game is arranged in a square grid, that would indicate 8 sheep. If the sheep are smaller than the avatar, a greater number of sheep and therefore levels are possible. At the end of the game, whether ended from the round loss condition or the game win condition, the user is displayed the average ratio of sheep lost per level.