Game of the Month
Meet Clyde the lovesick cricket in this fun-filled obstacle jumping game. Clyde must make his way through a booby-trapped factory to get to his true love, Cynthia. Crickets is from the master of Atari public domain programming, Stan Ockers. This BASIC program works on all Atari computers having 32K, with disk or cassette.
Clyde Cricket lives in a factory and is deeply enamored of Cynthia Cricket. He risks his life to bring her gifts, hoping to eventually win her feeler in marriage.
In order to deliver his gifts to the fair Cynthia, poor Clyde must jump between moving conveyor belts and avoid getting crushed by the objects upon the belts. He must also avoid touching any of the factory walls, floors, or ceilings-they've all been sprayed with a fierce anti-cricket poison.
To woo Cynthia successfully, Clyde must bring her flowers, perfume, candy, a necklace and finally...a ring. Each gift must be picked up at the center of the factory's lowest level and presented to Cynthia at her home on the uppermost level.
If Clyde fails, his three amorous brothers are ready to take his place. These Cricket brothers don't have to start at the beginning-they simply take over the current gift delivery. One last problem for Clyde-a jealous rejected suitor makes things difficult by throwing various objects from the top of the screen.
To make Clyde jump, you must move the joystick in the correct direction and simultaneously press the fire button.
You may use the [SELECT] button to choose a level of difficulty, the top ones border on the impossible. If you don't want so many, you can change the 7 in line 480 to a lower number.
Anyhow, time to get started. Type in Listing 1, CRICKETS.BAS, check it with TYPO II and SAVE a copy before you RUN it.
Player Missiles-The P/M area is made of strings, to allow easy vertical movement of players with string functions. The single line resolution P/M area is located on a 2K boundary by the string manipulation in line 150. Separate 256-byte strings are allocated for each of the players (PO$-P3$). The 1K unused space at the beginning of the area is used for screen data and assigned the sting DD$.
Joystick Routine-Line 510 has a USR function to call a machine language routine which allows jumping only when both stick and trigger are pressed. It is POKEd into string STK$ in lines 190-200.
Sound Routines-TWO sound routines are used, one with no amplitude change and the other with a decay in amplitude to sound like a piano. Both are inserted in the vertical blank process so as not to interfere with the timing of the BASIC program. They are POKEd into Page 6 using data in lines 1420-1450. The last 10 bytes in line 1450 insert the VBI routine.
Character Set-The character set has been extensively modified for using GR. 4 and GR. 5 graphics. It is first moved to RAM using a machine language moving routine read into ZZ$ in lines 1140-1160. It is moved to the top 1K of memory and RAMTOP is lowered 5 pages in line 1170. Character set data is POKEd in at lines 1180-1300.
Vertical Blank Interrupt-The vertical blank takes care of moving the conveyor belt by modifying the display list. Also the Cricket is also moved when on a belt and tune sounds are updated each VBI.
Display List- A new display list is built in Page 6 on line 1380 using data from lines 1390-1410. Lines 1460-1470 link the display list up to the screen data in DD$ (high order bytes). Lines 1480-1500 provide necessary data to allow the VBI to manipulate the low order bytes of load Memory Scan instructions in the display list.
This September Game of the Month is being published by Antic as a tribute to Stan Ockers-the best known programmer for the Atari. Many newer readers of Antic may not be familiar with Ockers. But his smooth, inventive games were a highlight of this magazine's early issues.
The Best of Antic anthology contains two Ockers games, Chicken and Bats. This book is available from the Antic Arcade Catalog in this issue, as are no less than FOUR public domain disks with Ockers games (PD001, PD003, PD004, PD005).
Ockers definitely has a unique way of doing things. He lives in Lockport, Illinois but his games usually make their first appearance in the newsletter of the Eugene Oregon Atari Computer Enthusiasts club. Ockers resists all offers to turn pro, he insists on keeping all his games (including this one) in public domain and won't accept payment for them.
Therefore, a few readers may have already seen Crickets on bulletin boards here and there. But many more of you will now have the pleasure of experiencing Stan Ockers' bold, clean game programming for the first time. -ANTIC ED
Listing: CRICKETS.BAS Download