Editing Asteroids (video game) (section)

===Implementation===
Logg modeled the player's ship, the five-button control scheme, and the game physics after ''Spacewar!'', which he had played as a student at the [[University of California, Berkeley]], but made several changes to improve playability. The ship was programmed into the hardware and rendered by the monitor, and it was configured to move with thrust and inertia.<ref name="WiredEdLogg"/><ref name="RetroGamerAsteroids"/><ref name="RulesOfPlay"/> The hyperspace button was not placed near Logg's right thumb, which he was dissatisfied with, as he had a problem "tak[ing] his hand off the thrust button".<ref name="RetroGamerAsteroids"/> Drawings of asteroids in various shapes were incorporated into the game.<ref name="EdgeAsteroids"/> Logg copied the idea of a high score table with initials from Exidy's ''[[Star Fire]]''.<ref name="RetroGamerAsteroids"/>

The two saucers were formulated to be different from each other. A steadily decreasing timer shortens intervals between saucer attacks to keep the player from not shooting asteroids and saucers.<ref name="RetroGamerAsteroids"/> A "heartbeat" soundtrack quickens as the game progresses.<ref name="AtariIncBIF">{{Cite book |last1=Vendel |first1=Curt |last2=Goldberg |first2=Marty |title=Atari Inc.: Business Is Fun |publisher=Syzygy Company Press |date=November 2012 |orig-year=1st. Pub. 2012|page=515 |chapter=Chapter 8 |isbn=9780985597405 |chapter-url=https://books.google.com/books?id=3FwGMtRafrAC&q=asteroids+heartbeat&pg=PA515 |name-list-style=amp}}</ref> The game does not have a sound chip. Allen created a hardware circuit for 13 sound effects by hand which was wired onto the board.<ref name="RetroGamerAsteroids"/>

A prototype of ''Asteroids'' was well received by several Atari staff and engineers, who "wander[ed] between labs, passing comment and stopping to play as they went". Logg was often asked when he would be leaving by employees eager to play the prototype, so he created a second prototype for staff to play.<ref name="RetroGamerAsteroids"/><ref name="ClassicGamingAsteroids"/> Atari tested the game in arcades in [[Sacramento, California]], and also observed players during focus group sessions at Atari. Players used to ''Spacewar!'' struggled to maintain grip on the thrust button and requested a joystick; players accustomed to ''[[Space Invaders]]'' noted they get no break in the game. Logg and other engineers observed proceedings and documented comments in four pages.<ref name="RetroGamerAsteroids"/>
<!-- HIDDEN BECAUSE OF NO EASY RELIABLE SOURCE: ''Asteroids'' uses 6 [[kilobyte|KB]] of [[Read-only memory|ROM]] code. Another 2 KB of vector ROM contains the descriptions of the main graphical elements (rocks, saucer, player's ship, explosion pictures, letters, and digits) in the form of DVG commands. For each picture frame, the 6502 writes graphics commands for the DVG into a defined area of [[RAM]] (the vector RAM) and then asks the DVG to draw the corresponding vector image on the screen. The DVG reads the commands and generates appropriate signals for the vector monitor. There are DVG commands for positioning the cathode ray, for drawing a line to a specified destination, calling a subroutine with further commands, and so on. It features various sound effects, each of which is implemented by its own circuitry. There are seven distinct audio circuits designed by Delman. The CPU activates these audio circuits (and other hardware components) by writing to special memory addresses (memory mapped ports). The inputs from the player's controls (buttons) are also mapped into the CPU [[address space]]. -->