Gorillas in 8086 assembly

GORILLA.BAS gameplay with fixed-point trajectories, incremental redraw and an optional computer opponent.

Gorillas filling the screen on a dark blue sky. At the top: Kong, Score 000 - 000, Angle 45, Velocity 70 and Wind +004. A yellow smiling sun hangs over a skyline of teal, grey and red buildings with lit windows, an orange gorilla stands on a roof at each end, and a small red arrow under the city points right. — Kong's turn, full-screen on VGA.

Players: 1-2
Executable: 16,206 bytes
Adapters: VGA / CGA / Hercules

01 / Adaptation and controls

Adaptation and controls

The implementation follows Microsoft's GORILLA.BAS rules and trajectory formula; the reference listing is retained in the source repository. It adds a computer opponent and selectable match length while keeping same-keyboard two-player play.

Angles and speeds are integers. Enter advances fields and throws; Tab switches fields; P pauses and F toggles full-screen. Gravity and wind feed the trajectory calculation. This is native code, not a BASIC runtime.

02 / Game sequence

Game sequence

The Gorillas window on the os8088 desktop, blue with a border of small red sparkles. It reads G O R I L L A S, After Microsoft QBasic 1990, and five lines of instructions ending Press any key for setup, with two orange gorillas between them. — Animated title sequence.

The Gorillas window showing GAME SETUP. It asks Name of Player 1 (10 characters), says Default: Player 1, and has Kong typed in. The bottom line reads Backspace: edit, Enter: next. — Match setup.

The Gorillas window reading G O R I L L A S, STARRING, Kong AND Computer, with two orange gorillas and the line Press any key to play, inside the sparkle border. — Player introduction.

The Gorillas window on the desktop with a match in progress: Kong, Score 000 - 000, Angle 45, Velocity 70 and Wind -004 at the top, the sun, a skyline of red, grey and teal buildings with a gorilla on each side, and a red arrow under the city pointing left. — Windowed colour rendering.

Gorillas full screen with a small yellow banana in the sky just left of the sun, above the skyline and both gorillas. The text at the top has gone. — Incremental banana redraw.

Gorillas full screen, paused. The top reads Computer, Score 000 - 001, and Paused. P or Enter to resume. A large orange blast fills the spot on the left rooftop where Kong stood; the computer's gorilla stands on the right. — Collision and scoring.

Gorillas full screen after the hit. The top reads Computer, Score 000 - 001, and Point! Next skyline shortly. A bite has been taken out of the left rooftop, and the gorilla on the right has one arm raised. — Victory animation with persistent terrain damage.

The final scorecard full screen, inside a border of red sparkles: GAME OVER!, Kong 000, Computer 001, Computer wins!, and Press any key for setup. — Completed one-point match.

03 / Physics and dirty rectangles

Physics and dirty rectangles

Fixed-point arithmetic and a sine table replace the BASIC floating-point trajectory. The comparison test permits 0.75 pixel deviation from the reference formula. Sprite save/restore limits a flight update to its affected rectangle; gorilla collision uses the visible pixels.

The recorded XT city-redraw times are below. Input repaint was reduced from an 881 ms first-digit update to 5.6 ms on VGA by redrawing only the edited field. These are measurements of that renderer and test configuration.

The computer player searches candidate velocities incrementally at a fixed 55-degree angle, then applies bounded error. Original tunes use the speaker; optional FM match music is separate.

Time to draw a new Gorillas city on a 4.77 MHz IBM PC
card	in a window	full screen
VGA	1.24 s	1.45 s
CGA	0.37 s	0.33 s
Hercules	0.47 s	0.52 s

04 / Differences from BASIC

Differences from BASIC

Whole-number angles and velocities only. Physics and timer quantisation are not bit-identical to QBasic output. Two human players share a keyboard; there is no link mode. CGA colour is available full-screen, while the desktop window is monochrome.

05 / Run Gorillas

Run Gorillas

Launch GORILLAS.O88 from GAMES. The 360KB distribution places it on games360.img; the larger software images, live media and The Wire also carry it.

Download os8088 Source The other programs