Game Development Reference
In-Depth Information
A passive obstacle impedes movement without actually threatening the avatar. To
get past a wall or a chasm, the player climbs over or jumps across. Obstacles can
also trap the avatar in a region with other dangers. Obstacles are usually, but not
always, indestructible.
A stationary danger attacks the avatar when she gets close to it but does not move
around the landscape. Examples of stationary dangers include electric fences,
swinging blades on a pendulum, or plants that bite. Some stationary dangers must
be attacked or destroyed to allow the avatar to pass by; others are indestructible
and must be treated like obstacles, so the avatar has to avoid or surmount them.
Active dangers, or enemies, attack the avatar, moving around in the landscape. In
old games, they often moved in a fixed pattern that the player could learn to avoid,
but in modern games, artificially intelligent enemies locate and pursue the avatar.
See Chapter 6, “Character Development,” for more information on designing
enemy characters.
WAVES
When enemies appear or attack in groups, usually groups of the same type or simi-
lar types of enemies, they are said to come in waves. The makeup of the wave
normally varies, including a selection of enemies appropriate to the current level of
the game. As the game progresses, the waves include stronger enemies. At later
stages of the game you may want to phase out the earlier weaker enemies, because
they will no longer provide an effective challenge. Enemies increase in strength
and number, reaching a peak at the end of the level.
Waves of enemies can appear in exactly the same way every time the player plays
(a scripted wave) or they may vary according to an algorithm that you design.
Scripted waves of enemies have appeared in games ranging from the original
Space
Invaders
to
Max Payne
and many others. In these types of games, you simply build
the size and composition of the wave into the level however you wish.
If you want waves of enemies to arrive according to an algorithm rather than in a
fixed progression, choose particular locations in the level (or time intervals in the
game) and a pool of enemy types from which to draw the enemies who will appear.
Design your algorithm to select a number of enemies consistent with the level of
the game and the difficulty setting, if there is one. You can implement a simple
form of dynamic difficulty adjustment by having your algorithm check the amount
of avatar lives or health points remaining; if the number is low, generate fewer ene-
mies or weaker ones.
TIP
The player won't
know the algorithm
that generates waves
of enemies and may
perceive their arrival
to be random. You
should not really
generate waves at
random, however,
or you risk creating
spikes or troughs in
the difficulty level.
THE BIG BOSS
In many games, a large enemy, or big boss, significantly harder to fight than any of
the previously encountered enemies, guards the end of a group of themed levels.
Defeating the boss takes the player to a new set of themed levels. Boss characters
