Sunday, 29 October 2017

RetroChallenge 2017/10: Gotcha

Okay, I didn't think I would have time for anything else for this month's RetroChallenge, but there was lots of curling going on this weekend, which my wife follows with a passion, so I found myself idly coding away while listening to the Masters (the TV's in our den). What I came up with was a program inspired by a real old game. I'm all the way back into the 1970s now scraping the bottom of the barrel for ideas. The game is called Gotcha. It's one of Atari's first video games. Apparently it wasn't all that popular. The original was two player.  Each player took turns chasing the other. This theme is reflected in its somewhat risque promotional material:
Don't know what's going on there.  In any case, the game mechanic involves a continuously changing maze. The logic of the mechanic of the change is difficult to discern, but I thought I might be able to recreate it, at least to some extent, on the MC-10:
Apparently the original game cabinet used some "breast" shaped cups as controllers.  After complaints Atari changed them to standard joysticks. Seems like a pretty blatant attempt at using sex to market a game to teenage boys, but it wasn't enough to overcome the mediocrity of the game.  It was no Pong. Here's another video of the original, but just the game play:
I changed the game to be single player. You move your cursor to collect coloured dots randomly placed on playing field. You have to avoid running into walls, or, because the walls are continuously redrawn, having the walls run into you.  There is a time limit, so you have to try to move fast.  Dots will move if you don't get them in time.They can also sometimes become enclosed by the walls of the changing maze.  Here is a video of what I managed to come up with.  I have tweaked it a little since making this video.  Now the changing walls can't erase the target dots.  I also have tried a technique of using a period to replace zero numeric constant in the draw statements, which I recall someone saying can make MS Basic run a little faster.  Not sure if it is true, but it doesn't seem any slower either.
So that definitely wraps it up for me for this Autumn' RetroChallenge.  Thanks to John again for organizing and to all the other participants for sharing their retrocomputing hobby.  I look forward to seeing what you folks get up to next year.

Sunday, 22 October 2017

RetroChallenge 2017/10: Dante's Run

This is a weird one. The inspiration for this new game came from a game for the Sinclair ZX81. I was watching a playthrough by Villordsutch of a game called TAI.  It is a Star Wars themed game.  You start by flying a ship through a tunnel in an asteroid. Except this tunnel is not filled with strange space creatures who might inhabit the insides a giant space worm living in the heart of an asteroid.  No, there is a giant skull with stacks of smaller skulls piled on top of it like some kind of Indiana Jones lost temple.  And that's not all.  The temple is protected by "ghost guards."  My first impression was that the game was creepy-temple-themed, but when you get through the cavern you switch to another screen in which you are the Millennium Falcon. A Tai fighter maneuvers around you and you must shoot it out of the sky/space. The mixture of motifs is very weird.
The creepy cavern of the skulls was certainly inspiring. I thought I could achieve the effect of flying upward through a maze using a string array and then just adjusting the pointer variable so you  see a window of the current 15 lines on screen. This way the ship could fly up "towards" the top of the screen instead of the more standard scrolling effect used in basic games that takes advantage of the automatic screen scroll that occurs when you print a line at the bottom of the screen. It turned out pretty well and is relatively speedy.  Now I have completed a Basic game that scrolls up to go along with my games that scroll right, such as Raider, and scroll down, such as my game Boarder (I'm not sure if I'm using the terms up/down left/right correctly--does the window scroll or the information being viewed by it?--I'll let you figure it out).

I thought I would try to create an even more creepy cavern effect. It's nearly Halloween, so I thought skulls and stuff would be neat. I decided as well to do it in the SG6 mode. This means the walls could be made out of the creepy neon mucus green solid character. The ship uses two other characters from the mostly useless lower 128 character set, which are really just random line patterns that represent bit numbers because no external character generator is wired to the MC6847 on the MC10. I chose a block character with two lines on each side for the base of the ship, and a narrow centred line for the "point" of the ship's nose.  The nose part is resilient (i.e. collision detection is only on the base section). 

As the game progressed I realized it was really a descent into hell theme I was developing with the extra graphics I was adding.  I also needed a "goal" stage to replace the Tai fighter-Millennium Falcon stage in the Sinclair game.  I decided to name the game "Dante's Run" and to make the transition stage a showdown with Beelzebub himself. I have been thinking for while I wanted to do a game where you have to shoot through counter rotating shields in order to try to hit the mother ship.  This is that motif, but with the Dark Lord as target. You have a limited time to break through the two fire shields and score a hit on Satan.  If you run out of time before you do, you start back in the cavern.  If you succeed, you score 2000 extra points and you get an extra life.  Your life is measured by the length of your laser when you shoot. You start with 5 lives. You lose a life when you hit one of the dark green guardian specters.  You die automatically if you hit any walls.  Your goal in the cavern is to collect the blue "purgatorial souls." You get 100 points for each one.  When you collect 1000 points you trigger the intermediate stage with Satan.  Shooting the specters can help get them out of your way, but it doesn't score you any points.  Just be careful not to shoot any of the purgatorial souls.  Doing so wont lose you any points,but it might upset the big guy upstairs!  Here's a vid:
I don't know if I'll have any time to do more stuff for RetroChallenge this month. It's mid-term time for me and the term will be heating up a bit for a while.  If I don't get the chance, I wish all my fellow contestants good luck as we head into the final stretch!

Tuesday, 17 October 2017

RetroChallenge 2017/10: Binary Room

Binary Land is a puzzle video game developed by Hudson Soft in 1983 for the MSX, FM-7 and NEC PC-6001. In the game players have to unite two characters (male and female), who are in love. The MSX version features a human boy and a human girl. The player controls the two characters simultaneously, with a timer adding to the difficulty. These characters move in mirror images of each other. The game features many different puzzles stages that the characters must navigate, and there are enemies within the mazes that add extra challenges.
The MSX Version with boy and girl characters
I found out about this game when I stumbled across a Japanese website dedicated to people's computing projects using arduinos and raspberry pie devices. Some of these devices implement versions of Basic to allow for simple programming projects in the style of old 8-bit computers.
This one seemed to display a simple text like game.  The author explained that they had created a puzzle game inspired by the game Binary Land.  He called his game Binary Room. I suspect this was because it involved a simple rectangle with some randomly placed blocks in it, rather than complex set puzzles/mazes.  The movement system was the same though, with two "characters" A and B being maneuvered in a mirror like fashion.  The object of the game was to move them so that they straddle numbers in sequence.  Each stage has a set of numbers equal to the stage number randomly placed in the room, up to stage 9.  Here's the source code for the game as listed by Taisuke Fukuno, who I take to be the programmer, although he might just be the person responsible for the "Create Everyday" website.
10 S=1 15 CLS:LC4,0:?"STAGE:";S
20 FOR I=0 TO 15
30 LC8+I,2:?"#":LC8+I,17:?"#"
50 LC8,2+I:?"#":LC23,2+I:?"#"
90 X=RND(12)+10:Y=RND(12)+4:IF SCR(X,Y) CONT
100 LCX,Y:IF I%3 ?"#" ELSE ?I/3
110 NEXT
120 X=15:Y=16:V=16:W=16:C=1:CLT 125 K=INKEY()
130 A=-(K=28)+(K=29):B=-(K=30)+(K=31)
140 IF SCR(X+A,Y+B)=0 LCX,Y:?CHR$(0):X=X+A:Y=Y+B
150 IF SCR(V-A,W+B)=0 LCV,W:?CHR$(0):V=V-A:W=W+B
160 LCX,Y:?"A":LCV,W:?"B" 165 LC(X+V)/2,(Y+W)/2:IF SCR()-48=C IF Y=W AND ABS(X-V)=2 OR X=V AND ABS(Y-W)=2 ?CHR$(0);:C=C+1:IF C=S+1 LC4,20:?"CLEAR!":WAIT30:IF S=9 END ELSE S=S+1:GOTO 15
170 LC16,0:?"TIME:";TICK()/60:WAIT3:GOTO 125
The questions marks represent PRINT commands.  The LCx,y commands are equivalent to PRINT@ or LOCATE commands in MS Basics.  SCR(x,y) commands do the job of checking the character values stored at specific screen locations.  The rest are pretty much standard Basic.

I found that the logic for placing the numbers was completely random, so sometimes they could be placed in a way, depending on where other numbers and blocks were placed, that there was not room on either side or above and below, to maneuver the characters around it to straddle it.  This would make a stage impossible to complete.  I changed the logic so that after placement, each number is checked to see if there are spaces to the right and left or above and below.  If not, the number is moved somewhere else and re-checked. This vastly decreased the possibility of generating incompletable stages, but not entirely.  Very occasionally you might end up with something like this:

#  #

The check shows that the top and bottom spaces are clear, but not really because the top space is not really accessible but has been blocked off to access by the character.  The number of blocks placed per round is equivalent to the number of the round multiplied by two, so this possibility is very rare.  Even on level nine there will only be 18 random blocks placed on screen.  But to prevent frustration I added the ability of the player to press R to redraw any stage and allow play to continue.  So check your stage before setting out!  The object of the game is to complete the 9 stages before 1000 seconds run out.  The faster you complete, the higher your score.  High score is saved.  When you complete the puzzle Beethoven's 'Ode to Joy' is played.  I tried to translate the music from an updated version that Taisuke also posted.  It's not a very good job, but my son Charlie is away at university, and he's my musical expert.  Perhaps when he comes back at Christmas I get him to take a listen and try to improve on my poor job.

Here's a video that Taisuke posted showing his updated version with music:
Here is a video of my port.  I have made some changes since making this video.  Now the counter counts down to zero and a higher score is the score with the most seconds left on the clock when stage 9 is completed, which is a bit more intuitive.  I also added the R redraw function to the instruction screen.

Anyway, hi to the folks doing the RetroChallenge 2017/10! I've been peeking around a little but hope to have some more time soon to check out the other projects being done.  If you are not one of the participants please check out the RetroChallenge website.

Sunday, 15 October 2017

RetroChallenge 2017/10: Zector Adventure

"Zector Adventure" is a text adventure program distributed by T&D Software in 1984. From a clue in the game itself it seems like the original programmer's name was Darrell Ulm and that he had subtitled it Adventure #1.  It is science fiction themed and based roughly on the original Star Wars film. You must escape from the Death Star with some battle plans that will help aid the rebel fleet defeat the station you are on.
The game has a handy "MAP" command
The original version was programmed for the TRS-80 Color Computer. It has a hires graphics "MAP" command that shows you your progress. In porting it to the MC-10 I had to change the map command to display a simple text graphics map instead.  I used a subroutine to translate the former graphic commands to insert into a text array space "O" characters for rooms and "-" and "!" characters for passages that you haven't explored yet.  I also added a circular "Death Star"graphic into which the unfolding map is inserted.

I also fixed up a tonne of spelling mistakes. So I guess you could call the MC-10 version a bit of a "fix" of the Coco version. The author, for example, had spelled the "examine" command as "exemine" and many of the words with "ie" were spelled with "ei" instead.  I suspect, he was a teen programmer.  The game is a lot like the classic game "Dog Star Adventure" written by Lance Micklus for TRS-80 and published in SoftSide magazine.  I have also ported that game to MC-10:
I played through Zector Adventure and created the following walkthrough, which has been posted on the CASA Solutions Archive website:



I hope you enjoy the Zector Adventure!

Friday, 6 October 2017

RetroChallenge 2017/10: Atanarjuat

This was just a silly little program I put together over the course of an evening. I don't know where the idea came from. Probably while browsing images of 8-bit Basic games.  I think I saw a picture of a simple maze that used the basic principle of alternating vertical lines with random hole put in them.  The thought struck me that the number of random passages would determine the difficulty of the maze. Then I thought, hey could an A.I. beat a human being in navigating such a maze?  I mean, it could be made to ruthlessly search for a way across as it moved up and down, but unlike a human it could not survey the maze as a whole to discern where the zones of parallel horizontal passages were most richly laid out and navigate towards them. So I made an A.I. that just moves up and down the passages seeking a way right.  It takes the first way it finds and continues right until blocked.  If it hits a block at top or bottom, it reverses directions and continues looking for a right passage. Of course, creating an algorithm that is fast took a little thinking, but I got one that allows plenty of time to pole the user for input so that navigation for the player is pretty smooth. The brute force of the computer provides a real challenge for a human player. I fiddled with the number of passages for each row to a point that I felt the game was challenging, but not impossible for a human to sometimes beat the computer. In future I might play a little with the variables that draw the maze and see if making more passages makes it much harder or easier to beat the computer.  I named the game after a legendary Inuit character "The Fast Runner" or Atanarjuat.  There is also a famous film made by an Inuit director of that name. The story originally centres on a clan feud and monumental revenge quest. So in my game I decided to add the feature of being able to hit space and lay down a "block", which can trap the computer player in a row if placed right.
I've managed 3 wins against the computer out of 5 but never higher than that. If you manage better hit the F11 key in the VMC10 emulator to take a screen shot, or snap a picture and send it to me!  Also, the program is small enough and simple enough to fit in 4K, so it's available for those MC-10ers out there who like using the real hardware, but who don't have a 16K RAM expansion.  Enjoy.