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Video Game Design Foundations
Two-dimensional (2D) games
have characters and backgrounds that play
in only two dimensions: length and width, as illustrated in Figure 4-19. A
character in a 2D game can only move up, down, left, or right to the limit of the
length and width of the game frame. This style of game has flat characters on a
flat background.
There are two terms commonly used to describe the presentation of a
2D game on the screen: game frame and visible play area. A
game frame
includes all of the items programmed for a complete scene or level of a
game. The game frame is the entire game world for that scene. This includes
items visible on screen and all items that exist off screen. The part of a
game frame that is displayed on the video screen is called the
visible play
area, stage, or
scope.
In addition to tracking off screen objects, the computer may also have to
scroll the game frame as the player moves.
Scrolling
is where the game frame
is moved so the position of the player is always in the visible play area. It is
important to remember that all objects on the game frame remain, even though
they are not visible. Refer to Figure 4-13.
Scrolling can easily be demonstrated using your hand and a textbook. The
textbook is the game frame and your hand is the visible play area. Lay your
hand on the textbook and move the book without moving your hand. That is
how the computer scrolls the larger game frame to present a moving view in
the visible play area.
A 2D character can be made into multiple poses to create a sprite character
set to display the movement animations used in the game. Recall from
Chapter 1 that a sprite is a 2D asset. A
sprite character set,
then, is a collection
of 2D assets, such as different poses, for a single character. As discussed earlier,
a sprite sheet contains the sprite character set. A sample sprite character set
from RPG Maker XP is shown in Figure 4-20. RPG Maker XP is a game engine
for developers creating role-playing games. Direction of travel for sprites is
typically defined by compass directions: North, South, East, and West. Some
sprite character sets can have 16 directions of motion just for walking on a flat
surface.
Two-Dimensional Games
Figure 4-19.
Flat shapes like those
shown above are
2D objects. They
have length (X) and
width (Y) dimensions
only.
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