Archive for March, 2018

28
Mar
18

Numjump for DOS

Today’s game is another homebrew made by Daniel Remar in 2017. It’s quite interesting as I’d describe it as a turn-based puzzle platform game, an odd combination indeed. He wrote it using QBasic and has included the source code along with some binaries compiled for 16bit MS-DOS as well as 64bit windows (using QB64 as the compiler).

In technical terms the game is fairly basic, it’s essentially using a 40×25 text mode with 16 colours and the PC speaker for sound. Whilst simple, it’s very effective, and the game is quite nice to look at for a text mode game. Sound is quite sparse, with few effects at all, but they are appropriate and don’t become annoying the way some games can become. Looking at the code, this could be ported to anything with a decent Basic interpreter and a 40 column display mode.

What makes the game odd and interesting is the mechanics of it. Your character only really has two goals, collect gold and reach the exit. In order to do this you need to jump around a small level avoiding obstacles that trap or kill you. The player moves one step at a time. The jump mechanic is a bit hard to describe. You have a maximum jump power, which is the number of steps you can travel vertically. For each step vertically you take you can take a step horizontally left or right. Once out of steps you must fall to the ground. You can fall at any time in the process by pressing the down arrow.

It’s a bit tricky at first, but once you get the hang of moving around it works quite well.

The level design works well with these mechanics to make for a challenging but not punishing experience. If you do happen to fall foul of a trap, the level is simply reset without any further penalty. The traps are fairly basic, there are spikes, Laser barriers that can be toggled, and some moving obstacles where timing is critical. Some areas can be inaccessible until you’ve increased your jump power, and others require a bit of thought to find your way in, but in general the puzzles are solvable in a reasonably short period without being easy.

Numjump is fairly short, you can finish it within an hour, but the length feels just about right. You get just enough of each type of hazard and puzzle to feel satisfied, but not so much as to become repetitive. If you’ve finished the game, you can go looking for all the secret dots, or make an attempt at collecting all the gold for the reward of a secret level, one for each achievement. It’s fun and well designed, so I’d say it’s definitely worth a go. I downloaded it from the Dos Haven site here, the official site there is linked to the authors twitter account.

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20
Mar
18

Trying the Campbell Cassette Interface

Some time ago I acquired an interesting bit of vintage tech, the Campbell Scientific C20 cassette interface. Since then it had been sitting on my bench looking lonely, I decided that I should at least try it out before I salvage any of the many useful chips it has inside. I have found a user manual for it along with information confirming that it is indeed what I thought it was, an interface for reading data encoded on audio cassettes by data loggers.

Not having any audio cassettes with appropriately encoded data however created a very simple issue. How exactly should I get it to do anything at all? It turns out whilst the C20 is primarily designed for reading from tape, it is possible to get it to write one as well, I thought we might as well look at the encoding on my oscilloscope and record a sample of the audio.

So I connected my oscilloscope to the output and a serial line to my old MS-DOS machine. After twiddling with the serial settings both on the machine and in Kermit I managed to get a welcome message and menu from the device which confirms that at least the CPU and serial lines are working. Unfortunately this is about as far as I have gotten.

The manual is exceptionally useful, providing not only information about basic use, but also more detailed technical information and example programs in basic for operating the device. I’ve translated one of these programs for writing data to tape, it seems the device is receiving the data I’m sending, but nothing appears on the output that I can see. I’ve not worked out if it’s something as simple as not connecting the scope correctly or if there is some hardware failure.

So unfortunately not as much to report as I’d like, but time has been quite limited and something is better than nothing. I’ll keep trying in the short term.




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