Space Fever

Space Fever is Nintendo's attempt at a Space Invaders clone, but at least they were nice enough to put in three different modes of play.

Revision Differences#

There are three different versions in the MAME romset: spacefev (New), spacefevo (Older), and spacefevo2 (Oldest).

The game changes the fire delay of the invaders based on the player's score. The delay decreases when the player's score is greater or equal to 300, 1100, 2100, 3100:

Default	300	1100	2100	3100
56 frames	16 frames	11 frames	8 frames	6 frames

: In the new version, the highest point threshold is changed to 5100 points.

The delay changes again after the player has at least 10,000 points. In the oldest version, the game will just stop checking the score, but since the delay has to be rechecked and set every frame, what ends up happening is that the delay changes from 6 frames to the default 56 frames.

: In the other versions, once the player has at least 10,000 points, the delay is set to 4 frames.

The method the games uses to calculate the UFO bonus is different in the oldest version. In that version, RAM address 608D is a pointer to a UFO bonus table. That RAM address is incremented every time one of the player's shots hits something, which includes the shields at the bottom and the top of the screen. The pointer always starts at 18C8.

: Note that this is the same basic method that Space Invaders used, and a lot of values in the tables are the same:

Space Invaders	100	50	50	100	150	100	100	50	300	100	100	100	50	150	100	50
Space Fever	150	300	50	100	150	100	100	150	300	50	100	150	50	150	100	300

: In other versions, the UFO bonus is determined by the value of universal game timer (60C0) at the time the UFO was hit, modulo 4:

0	1	2	3
50	100	150	300

Old	New

The "TOP" score text is 8 pixels lower in spacefev and spacefevo.

Old	New

In the oldest version, the explosion animation has two frames, but they're identical. The other versions fix this by changing the second frame.

(Source: Original TCRF research)