Rock Crush For The ZX81!
This is the original version of Rock Crush by Steven McDonald.

It was always thought the ZX81 couldn't achieve High Res Graphics like the ZX Spectrum had for example. All the ZX81 games used standard character set graphics such as scary capital O's chasing you around a maze and an asterisk * or --> would do as an incoming firebomb and arrow respectively whilst a $ sign made a nice guard with a spear!

Indeed.. it is true the machine cannot do High Res Graphics - without additional hardware that is. Instead, advantage was taken of the fact that there is no dedicated video chip on the ZX81 as such. It is in fact a clever combination of carefully timed hardware (ULA) and software that work together to drive the TV picture in real time. With some custom programming of the video generation routines - it is possible to achieve what is known as Pseudo High Res.

To all extents and purposes it looks just like a ZX Spectrum quality display - it's all smoke and mirrors really but it is highly effective and no extra hardware other than the standard 16K RAM pack was required.

Hear the original 1986 radio review by John Stewart broadcast on WOAI 1200, Texas below:
Rock Crush
Rock Crush came out in 1985 on the standard ZX81 with 16K RAM pack. It utilised a pseudo high res display and as such really stood out from the crowd. Even if I say so myself, it looks quite good on that machine to this day!
16K ZX81
The standard ZX81 came with 1K of RAM. For serious applications you could boost it all the way to 16K and almost every user did! Manufactured by Timex in their Dundee factory for Sinclair. There were UK and US models.
Dan's Revenge
Dan's Revenge came out in 1986 and was the sequel game. This time Dan had to get to the exit Door, collecting diamonds as he went whilst avoiding the beasties out to get him!
There is no 35th Anniversary Edition of Dan's Revenge yet! but never say never!
Rock Crush
This is the cassette for Rock Crush. These were available for sale during the mid to late 80's. Some were flown over the pond to increase awareness of the game and help get the word out.
Game Hints
The first level always seems to trap people. The key to it is to work on the right hand side of the screen and drop the large stack of rocks but quickly run right. This player has ran left and won't complete the level!
Dan's Revenge
This is the cassette for Dan's Revenge, the follow up game to Rock Crush. Again, it was available commercially at the time (1986) and some copies were flown abroad for publicity.
Below: The original 1985 design of the first level. Follow the numbered moves in pen to get through the level easier!
I would say that Rock Crush's best point is the screen level design, which even today, I like to see people puzzle over. I would have liked a stronger end seqence etc. but I was very happy with the finished program size - it had fit into 16K. For a long time, there was only one level and then the game crashed. It wasn't a bug, just I hadn't designed any more than one level at the time. My inspiration for the game came from an advert in Your Computer for a game called 'Diamonds' by Simon Hunt for the 16K Atari XE/XL - English Software (1983). To this day, I have never actually played this game but I did watch someone on YouTube play it on an emulator a few years back and the gameplay wasn't what I had imagined. For me it was this single screenshot in the advert that inspired me - the design and colours of it - even though I was working in black and white. (It is interesting to me now to note his follow up game from 1984 was entitled 'Dan Strikes Back'!) The other obvious inspiration was my friend Scott Dolan's Commodore 64 and his copy of a certain boulder moving game... Rock Crush does have very different gameplay however - much more puzzle oriented. Think before you move!
Watch Villordsutch's Video Review of Rock Crush 16K (1985) below:
The original game loaded in 5 parts as it wasn't possible to develop the game with the Z-80 source code, my assembler, and the object code all at one time in 16K. Instead it was developed in separate parts - each of which loaded into its own section of memory and was developed independently. Once all parts were loaded - the high res screen with title graphics pre-loaded, the level data, the graphics data etc, the main game code section loaded.

Over the years various releases have played about with the game timings - mainly due to them not running at the same speed as the original when used on ZX81 Emulators. Time has passed however and modern emulators now run everything almost perfectly so no need for this nonsense anymore!

This always annoyed me so I spent some time during 2018 putting all this right and doing a one piece remaster. You can download these from this website below. The follow up game Dan's Revenge also suffered from the same fate, so I updated it as well. These new versions have never been publicly released for download before.

They were however included (exclusively) in Kevin Palser's iOS ZX81 emulator. Please do not distribute them with other ZX81 emulators, archive packages etc. They are available only from this website and I retain the copyright on their distribution.

Thank You.

Whats New In This Version?

* All previous ZX81 releases officially retired.

* A new fresh master loaded in from the original Duplicating Master Tapes.

* Nothing modified regarding original game code/play feel/timings etc.

* A new routine added and documented here to allow a one-part load.

* This new routine manages moving memory about but does not interfere with the operation of the game itself and indeed goes to great lengths to leave the machine in the same state as the original 5-part load.

* Documentation updated.
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