Remake of the ZX Spectrum game for the Apple II.
Updates: i. 30 April 2021 - I Sped up rendering for a more even experience, especially in The Vat and The Warehouse. The Apple II vesrsion is marginally slower than the ZX Spectrum version (I think - tested with Speccy) but feels pretty good. To make room for the fully unrolled level rendering, I sacrificed the lower case letters in the font. I updated the table of timings, below.
This is a game I have always loved, from the moment I saw it in a computer shop back in the 80's. I once made an okay Commodore 64 version, in C, but this version is a rewrite from the ground up for the Apple II, in 6502 assembly language and I am very pleased with the outcome.
This is my first color program for the Apple II. Another learning experience :)
- CURRENT STATUS
The game is complete.
There's a pre-built Apple II disk of the project, mminer.dsk under the releases tab. This can be played directly in emulators.
There's also a video of the game here: https://youtu.be/OGxj_g1ImhM
- DIFFERENCES FROM THE ORIGINAL
There are several differences that all have to do with Apple II hardware limitations.
In the Apple II version, the title screen is not the high resolution picture with the animated piano keyboard. Instead it uses the ZX Spectrum loading screen, which has the words Manic and Miner bounce up and down. I do use the hires screen for loading though, so it is just the opposite way ;)
The reason for not using the high resolution picture is due to a memory limitation. If I did use some of the ROM memory for RAM, I could probably fix this, but I didn't want to trash ProDOS and I didn't want to have to reboot the Apple II when the program is quit.
The biggest differences have to do with the screen and keys.
The ZX Spectrum has a 32 column, 8 pixel per column, color display (256 pixels). The Apple II can only display 20 7-pixel color columns (140 pixels). This means I cannot fit the level on-screen at any given time. The level does need to scroll as you play through it.
I have settled on a 3 zone scrolling method. As Willy enters a zone, the screen will quickly scroll to the proper "camera position" for the zone Willy is in. However, if you press the C key, the scrolling method toggles to one where the game tries to keep Willy more or less in the middle of the screen - so as you move around the center of the room, the game scrolls the screen all the time. This method may be better suited to learning a room.
The scrolling method I use scrolls the game in "game columns" which means 2 bytes at a time. This is a rather coarse scroll. I did spend a lot of effort on making run-time duplicates off all instanced data that allowed me to do a 1-byte scroll. Sadly, this turned out to be even worse as the motion became very jerky a lot more frequently.
For the curious - if you want to draw a green line on the Apple II, starting at column 0, for 7 pixels, you need to write the following 2 bytes (bit representation): %00101010 %01010101. However, if you want that green line starting at column 1, you need to write the bytes in the other order, i.e. %01010101 %00101010. To get the speed I need, I have all data to be rendered stored as instances that I can "blast" to the screen quickly. For a 1-byte scroll, the whole screen needs to be rendered with the image bytes reversed, so I needed more memory to make the reverse second set. And then that didn't pay off :(
About the keys - The ZX Spectrum version requires keys to be held down to move. The Apple II doesn't have a concept of keys being held down. You only know when a key is pressed, not when it's released so you cannot tell what state a key is in. You can also only detect one key press at a time.
In order to make the game play with the key limitation, I use the keys as toggles. If you press P, Willy will start and keep walking, as though you are keeping the key down. Pressing P again will stop Willy, as though you had let go of the P key. My Apple IIe does have auto-repeat so actually holding down the P key has an undesirable effect of stutter-walking.
I also made the game remember keys so that you can anticipate a key-press (like you would steer early in Pac Man). This works very well but it can also cause grief. For example, if you press Jump while in a jump, but you land somewhere unexpected, you will still jump because of the stored anticipated jump. If, of course, you are quick enough, just pressing the key again before it activates would cancel the anticipation.
All in all, the key and scroll system makes the game fun and playable, I think, as much as is possible given the limitations.
- TECHNICAL DETAILS
The game is written in 6502 assembly language using the ca65 assembler. The game uses memory from $0800 to $BE4B.
Below is a CPU cycle profile of 1 game frame in stage 1 after a couple of seconds of being on the level. The door isn't visible so this renders only the one enemy and Willy, as well as the level tiles. gameDelay is an artificial delay based on how many tiles were rendered, which smooths out the gameplay, and thus song tempo across levels. If the music is turned off, audioPlayNote will also create an artificial delay to simulate the delay incurred by toggling the speaker.
Cycle counts are not constant across all frames so all timings below are approximate.
As can be seen, clearing the area where the world will be drawn takes almost 32% of the frame and drawing the level tiles takes about 39%, plus 3% to re-render willy, of the total frame. Drawing is almost 80% of the frame.
The ZX Spectrum version had Willy under the level tiles, but I prefer Willy in front, so I re-render willy without collision detection once the level tiles have been drawn, so he is always in front (but before the door is drawn so he is behind the door).
After the intro music on the title screen, the game has a scrolling ticker that shows help and keys, but these are the keys:
- Q or O - Move Willy left
- W or P - Move Willy right
- Space - Jump
- B - Toggle Black and White / Color mode
- C - Toggle scrolling mode
- M - Turn the music on/off
- S - Turn in-game audio on/off
- ESC - Quit level or in UI, return to ProDOS
The game also supports the cheat mode, as in the original. In game, enter the cheat code 6031769 and a boot will appear next to the lives at the bottom of the screen. Cheat mode is now enabled. Press the 6 key to start the cheat. Now use the keys 12345 to enter the binary value for the level (0 through 19). Key one sets bit 0, so it's reversed.
Once the appropriate room has been selected, press 6 again to start playing that level. Note that the cheat cannot be turned off and also that the Game Win Sequence (once you beat the last level) is disabled if you cheated. To see that, you really have to beat all levels!
Here's a "cheat sheet" for the binary to access a level. If you enter a room number greater than 20, the room is reset to room 0.
|Cheat Key (binary 0-19 reverse)||12345|
|The Cold Room||10000|
|Abandoned Uranium Workings||11000|
|Miner Willy meets the Kong||11100|
|The Endorian Forest||10010|
|Attack of the Mutant Telephones||01010|
|Return of the Alien Kong Beast||11010|
|Skylab Landing Bay||10110|
|The Sixteenth Cavern||11110|
|Solar Power Generator||01001|
|The Final Barrier||11001|
- THE FILES
I tried to thoroughly comment all the code.
There are actually 2 programs in this. The 1st is the game, and it's in src/apple2.
|audio.inc||Routines to make the speaker beep|
|defs.inc||Constants and definitions used throughout|
|game.inc||The in-game logic, AI etc. The bulk of the "game"|
|input.inc||User controls for game and editor|
|level.inc||Decompress a level and place the keys|
|logo.hgr||8Kb splash screen in HGR format|
|logo.inc||File that simply does an incbin on logo.hgr|
|mminer.asm||Where the game starts, initial setup, etc.|
|mminer.cfg||ca65 configuration file|
|roaudio.inc||Frequency and timing data for music and SFX|
|rofont.inc||A ZX Spectrum font|
|rolevels.inc||Level layout, tile usage, sprite positions, etc.|
|rosystem.inc||Helper tables (multiplication, color masks, etc.)|
|rotext.inc||All text used in the game|
|rotiles.inc||Background tile definitions|
|screen.inc||Code related to drawing tiles, sprites, etc.|
|sprite.inc||Code for making instances of sprites, coloring them, etc.|
|text.inc||In game text and print functions|
|ui.inc||User facing screens (title, scroller)|
|variables.inc||All variables (scores, instance buffers, positions, etc.)|
|Willy.inc||All logic relating to the movement of the main character, Willy|
The second is the ProDOS loader that will auto-load the game. It's in the src/apple2.loader folder. It has these files (all provided to me by Oliver Schmidt)
|loader.cfg||ca65 configuration file|
|loader.s||file to load and start the game|
- BUILDING THE GAME
Making the game has a few steps. Use make and the Makefile on all OSs, that would be the easiest.
Start by making the loader - this needs to be done once only. make TARGETS=apple2.loader
Next, make the game with: make
The next step is to make a bootable disk image. For this, you will need 3rd party software. I use AppleCommander. This software will put the loader and game into the disk image. You will need to install Java to use AppleCommander.
The apple2/template.dsk is a "blank ProDOS floppy" that has the loader and the game placed on it by AppleCommander.
To make the disc image, set an environment variable to point at apple commander (see notes) and then use the command: make dsk
This will make a disc named mminer.dsk which can be loaded up in an emulator.
If you want to edit the code and get into some iterative development/testing, you can edit the Makefile. Look for, and change, apple2_EMUCMD. It is currently configured to work with AppleWin and the path to AppleWin is expected to be in an environment variable called APPLEWIN_HOME. Edit variables as necessary.
If you use AppleWin and you have sed installed, you can also uncomment the PREEMUCMD := sed... command which will copy the game symbols to the emulator for use. For that to really make sense, you should to do this make command once: make OPTIONS=mapfile,labelfile,listing,debugfile. That will make a file called Makefile.options that will be re-used, and will generate a label file with all the labels.
Once done, you can build and play the game with the command: make dsk test
- Find AppleCommander here (I used Version 1.6.0): https://github.com/AppleCommander/AppleCommander/releases
- Set the environment variable (or change the Makefile-dsk.md) to point at the apple commander jar file. Here's how it's done for different shell's: Powershell: $env:AC = "path to apple commander.jar" cmd.exe set AC="path to apple commander.jar" bash (Unix or MacOS terminal): export AC="path to apple commander.jar"
- Matthew Smith and BUG-BYTE for creating and publishing the game in 1983. Matthew later re-released the game with minor tweaks under the Software Projects banner. This is not that version.
- A special call-out to Oliver Schmidt who provided me with invaluable advice and support.
- Bill Buckels for Bmb2HDR which I used to make the logo HGR from my GIMP exported BMP.
- Everyone involved in the Apple II projects (AppleWin | AppleCommander).
- Everyone involved in making the cc65 tools, it's very good.
- Ian Brumby for showing me how you really unroll a draw loop.
Feel free to contact me at email@example.com if you have thoughts or suggestions.
Thank you Stefan Wessels 21 April 2020 - Initial Revision