INTRODUCTION
Rock Crush was originally devised and written for the 16K ZX81 by Steven McDonald in 1985. A re-mastered Definitive Edition version of the game, along with a belated sequel featuring expanded functionality and support for colour via the Chroma 81 interface is available from Steven's Rock Crush website.
In 2021 I was seeking an idea for a 16K pseudo high resolution flicker-free game for the ZX80 and felt that the nature of Rock Crush lent itself very well to the constraints of the flicker-free mechanism. I contacted Steven to see if he would mind and he gave permission to adapt the game as I saw fit. This page presents the results.
The limitations of the flicker-free mechanism meant that to re-use the original ZX81 game code was not viable. It therefore had to all be written from scratch. The ZX80 code was written completely from scratch, with the new levels provided by Steven himself.
Since the pseudo hi-res pixel patterns available from the ZX80 would not be the identical as those from the ZX81, an exact duplication of the original game's graphics would not be possible. So instead I decided to design all graphics from scratch, allowing the available pixel patterns to be used to their best effect. The meant that the functionality of the game would be very reminiscent of the original but the look and feel would be specific to the ZX80.
With the imminent release of Chroma 80, I wanted the game to include support for colour if the interface was detected. At startup, a check is made for the presence of Chroma colour facilities and if available then both lo-res and hi-res screens will be displayed in colour.
As with my other ZX80 games, I wanted the game to be available for both the 4K ROM ZX80 and 8K ROM ZX80, and both versions should visually look similar to each other. I therefore designed graphics that would (by and large) be identical using the pixel patterns available from both ROMs. But inevitably some deviations had to be tolerated due to some of the desired pixel patterns not being available from one or other ROM. Therefore the graphics displayed by the two ROM versions look very similar to each other but are not completely identical.
By the time the game was finalised, I had not long devised the Dual ROM Loading technique that allowed a single program file to be loaded using either ROM. This allowed Rock Crush 80 to become the first game to utilise this technique.
APPEARANCE
A continuous display is maintained throughout the title, menu and game screens, but a momentary flicker will occur when transitioning between lo-res and hi-res screens.
Screenshots of the 4K ROM version (with and without Chroma colour support) are shown below:
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| Title Screen (4K ROM) |
Menu Screen (4K ROM) |
Game Screen (4K ROM) |
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| Title Screen - Chroma (4K ROM) |
Menu Screen - Chroma (4K ROM) |
Game Screen - Chroma (4K ROM) |
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Screenshots of the 8K ROM version (with and without Chroma colour support) are shown below:
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| Title Screen (8K ROM) |
Menu Screen (8K ROM) |
Game Screen (8K ROM) |
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| Title Screen - Chroma (8K ROM) |
Menu Screen - Chroma (8K ROM) |
Game Screen - Chroma (8K ROM) |
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DESCRIPTION
The aim of Rock Crush is quite simple - move around the screen, digging out the earth to collect the diamonds. Once all diamonds have been collected, you move onto the next sheet and must do the same there. But each sheet not only contains diamonds and earth but also rocks. Dig the earth or collect a diamond from underneath a rock and that rock will soon fall down. So if you linger too long directly underneath a rock then you will be crushed. To collect every diamond you must work out a route that doesn't result in the rocks falling and blocking you from reaching the remaining diamonds. Digging earth also scores points and a bonus will be awarded for clearing all the earth from a sheet. So even more careful planning of the route to take is required if you wish to score top points. Luckily there isn't a time limit to each sheet and so you can progress at your own pace. Sounds simple, doesn't it?
ENHANCEMENTS
A number of enhancements were introduced over the original ZX81 version:
- The original ZX81 Rock Crush had 10 sheets to complete; Rock Crush 80 extends this to 50 sheets, with the new layouts devised and provided by Steven himself for the ZX80 release.
- The movement of the player is animated to show him running (in the original version the player just hopped to the new position).
- After completing a sheet, a bonus is awarded based on the number of lives remaining.
- Digging all earth prior to collecting the last diamond is now possible on every sheet, and doing so is rewarded with an additional bonus.
- At the end of a game, the score achieved is calculated as a percent of the maximum possible score.
CONTROLS
The following controls are supported:
- Keys 5, 6, 7, 8 and 0 (Cursor).
- Keys 6, 7, 8, 9, 0 (Sinclair).
- Keys Q, A, O, P and M.
- Keys Z, X, P, L and M.
- ZXpand joystick.
- Chroma 80 / Kempston joystick.
Holding the 'fire' button/key for 1 second will abandon the current life. Pressing SHIFT and SPACE will abandon the game.
SCORING
Points are awarded as follows:
| Digging earth | 1 |
| Collecting a diamond | 25 |
| Digging all earth | 100 per life remaining |
| Collecting all diamonds | 200 per life remaining |
| Completing all 50 sheets | 2000 per life remaining |
RELEASE
The game is initially being made available as a cassette only release, using an inlay style to match the Pacman and Kong releases made by Cronosoft. A photo of the Rock Crush 80 cassette can be seen below:
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Please email me if you are interested to obtain a copy of the cassette.