The idea of the graphic designer (Diseña) was to have a tool to be able to properly design the graphics for the games he was going to program in the future.

It is programmed in Assembler Z-80.

I finished programming it after two intensive months of development.

It's the most profitable program I've programmed, thanks to its usefulness and the number of times I've used it.

With it, you could design presentation screens, sprites, and game characters.

You can see a video of the program working Demo video

There's also a demo showing the best screenshots and graphics I designed with it: Video of the best screens

I programmed the Zodia spaceship game inspired by Konami's scrolling spaceship games.

It is programmed in Assembler Z-80.

It is dedicated to my math teacher (J. R. M. - José Ramón Molina), for giving me the idea of learning assembler.

The game is on SCREEN 1, with lighter graphics than SCREEN 2.

To give you an idea of what things were like...

Obviously, at some point the score achieved by the player had to be printed...

The numbers were either equivalent to uint8 or uint16

For the scoreboard, I chose the uint16 type (it couldn't exceed 65535)

To print the digits, the number had to be converted to Base-10, which I did by dividing by 10 n times, taking the moduli and quotients.

But... the Z-80 didn't have any instructions in Assembler for multiplying or dividing!! And now what?

Well, it's easy... we divide, subtracting the divisor from the dividend N times, and we increase the quotient as long as the result doesn't overflow...

How tacky!

Well, that's how things were...

There is a video that shows the complete scroll (with some errors): Full scroll video

You can see a video of the program working Demo video

After finishing high school, I wanted to try my programming skills in assembly language again.

The objective was to program a synthesizer adapted to the MSX sound chip (with three voices, and applying reverb effects (rapidly changing (manually) the emitted frequency for each pressed note), and turning off the note when the key was released.

The state of three synthesizer keys pressed at the same time (the three voices of the chip) was remembered.

I also wanted to make use of the frequencies associated with each note, which I found hardcoded in an area of the MSX ROM during a search.

To perform the search, I proceeded, simply knowing the frequency of the note A ((tuning fork) 400 Hz, and applying a root-twelve factor of 2 (2 ^ (1/12)) (one octave, twelve semitones)).

And then searching for the corresponding elements in the ROM, with uint16 type numbers.

You can see a video of the program working Demo video

During the summer between my senior year of secondary school and my first year of Teleco (1991), I worked intensively as a waiter at Bar Argente's in Salou.

I took the bus back and forth, and on the way back, before heading home, I would stop by an arcade to play a few games of the fabulous Tetris...

After more than 60 games of that game, I became an expert, and I loved finding that game when fate took me by chance to a place where there were arcade machines.

In 1992, I decided to program my version of Tetris, in Assembler Z-80 and in the record time of three days.

At that time, I had already flirted a bit with the digitization of sounds (from the MSX tape), and on the game's standby screen, a song is played through the speaker. (the openMSX emulator perfectly emulates that detail).

You can see a video of the program working Demo video

I don't remember when I first came across the possibility of digitizing sounds from the MSX tape.

But I do remember that I didn't even know what frequency I was sampling at... I just put a delay loop between samples for digitization, and the same delay loop for playback through the speaker.

I found that when that delay was too large, the sound didn't reproduce well. Later, I learned through sampling theory that this effect was known as aliasing.

From a television series I liked, I got the idea that a computer could "pronounce" a sentence chosen by the user.

So, with the new toy of digitization, I set out to obtain all the phonemes by digitizing my own voice.

The next step would be to go through the letters of a sentence, separate it into phonemes, and emit each phoneme in turn.

Yeah, a bit tacky... But it didn't give any more...

I programmed the rules of Spanish phonetics in an Assembler Z-80 application, with the interaction with the user by asking for the sentence in BASIC.

With the openMSX emulator you can perfectly emulate the execution of that little program.

You can see a video of the program working Demo video

Well, after spending countless hours playing The Maze of Galious, I decided to create a maze game inspired by it, and with a very similar visual appearance (with my limitations).

The program was again in Assembler Z-80.

I created the screens (in a 14 x 12 screen matrix) based on 4x4 character blocks that were combined like a puzzle.

So, a screen occupied 5 x 8 = 40 bytes, although a fixed memory occupation had to be added to define the 4 x 4 blocks.

I rescued several implementations to move the character around the world, although the most complete one ('PERFEC'), I couldn't get it to work in the emulator.

I think it has to do with the fact that the source code in assembly took up too much space, and conflicted with the area BASIC data, and the assembler, under those conditions, refused to assemble the program.

I remember that one day I had to do the trick of moving the BASIC memory area higher (with some wonderful pokes that I no longer remember).

And without them, there is no way to make that implementation work (although that source code was extracted correctly in the .cas).

You can see a video of the program working Demo video

The assembler is a fundamental part of developing in Assembler Z-80.

I bought the devpack from hisoft and made the most of it, making intensive use of it.

There was also a monitor, but I never knew how to get it to work...

In the video you can see an example of a session with the assembler Demo video