Tachikoma
13f1df03ef
Adding native RND and ASC (ae2c702) made RND a function name, and a suffixed
identifier that collides with one is refused -- "SYNTAX ERROR Reserved word in
variable name". Three example programs held their PRNG output in a variable
called RND#, or a host field called RND%, and none of them had run since:
- examples/galaga/ bound RND% as a host field on both ENEMY and GAME. The
BASIC-visible name is ROLL% now; the C member stays `rnd`. This one was
caught by example_galaga and example_galaga_interop, which have been
failing.
- examples/breakout/characters/breakout.bas and examples/megademo/
megademo.bas both use RND# for their LCG output, renamed to ROLL#. Neither
is in any test, so neither failure was visible.
examples/breakout/sprites/breakout.bas was broken a second way: seven REM lines
the reader refuses. Worth recording that the ceiling is not the one the message
names -- src/sink_stdio.c fails when the read filled the buffer without seeing
a terminator, so with AKBASIC_MAX_LINE_LENGTH at 80 the message says "79
character limit" and the real maximum is 78, because a 79-character line leaves
no room for the newline. The sweeps that fixed the corpus and the megademo for
this did not reach this file. The seven comments are reflowed.
The prose went stale with the code. Chapter 21 said "there is no RND verb in
this dialect; issue #16 tracks adding one", chapter 17's historical aside
offered an LCG that no longer parses, and four REM blocks across the two games
said the same thing. All of them now say RND exists, and say why these programs
keep their own generator anyway: the sequence has to be reproducible for a
headless run to be the same game on every machine, which is what lets
interop_test.c assert exact counts.
Chapter 21 also gains the rule that bit them, since a reader writing a host
type will hit it: a host field name is a bare word and shares a namespace with
every verb and function.
None of this came from the submodule bump -- all three were already broken on
main. It was found by running the tutorial games, which nothing else does;
that gap is akbasic issue #58.
Verified: all three run clean under the dummy drivers, and 114/114 default,
116/116 with akgl.
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
Co-Authored-By: Claude Code (Claude Opus 5, claude-opus-5[1m]) <noreply@anthropic.com>
Breakout, with artwork
Breakout, written entirely in BASIC for the AKGL BASIC interpreter, using downloaded CC0
sprite artwork for the paddles, the balls and the powerup gems. The bricks, the HUD and
the lettering are drawn — WINDOW moves the text layer to two rows at the bottom, and
everything the program draws then stays on the screen without being redrawn or captured.
The bricks are also collidable without being sprites: SOLID registers a rectangle
the interpreter collides against, so sixty of them cost none of the eight slots.
../../../build-akgl/basic breakout.bas
It needs the SDL build. Without a graphics device the first SPRSAV refuses by name and
the program stops there, which is the right thing for it to do.
| Key | Does |
|---|---|
| left / right | move the paddle |
| space | start a game, launch the ball, release a stuck ball |
| P | pause |
| S | sound on and off |
| Q or escape | quit |
Three lives, six rows of bricks worth 60 down to 10 points a row, and a field that cycles six rows, then five, then four while the ball gets faster every level up to a ceiling. A gem is worth 50 on top of whatever it does.
The powerups
A broken brick drops a gem about one time in seven, and only ever one at a time. Catch it with the paddle. The colour of the gem is what tells you which it is; the banner that flashes over the field names it as well.
| Gem | Name | Does | For |
|---|---|---|---|
| red | EXPAND | doubles the paddle's width | 20 seconds |
| yellow | MULTI | throws two more balls off the one in play | until they are lost |
| green | SLOW | drops the ball's speed to about two thirds | 16 seconds |
| blue | STICKY | the ball sticks where it lands; space fires it | 18 seconds |
| purple | CATCH | a second bar appears higher up the field | 24 seconds |
The second bar mirrors the paddle rather than following it, so it covers the side you just left. A second bar directly above the first is worth nothing; a mirrored one turns a dive across the field into a save at both ends.
How it works, and how to write your own
Chapter 18 of the guide builds this program step by step: loading artwork, budgeting the eight sprite slots, taking the text layer out of the way so a drawing can be seen, stamping the brick field, registering the bricks as collision geometry, the stroke font, the bounce without a square root, and the gems.
Chapter 17 does the same for
../characters, which builds the same game out of the text grid and two
DATA sprites — a completely different program, and the shorter one to read first.
Where the artwork came from
Kenney's Puzzle Pack 1, released under
CC0. The files in art/ are the
pack's own PNG/Default/ versions, unmodified, with the pack's licence file beside them.
art/PROVENANCE.md says which file is used for what and why the double-size set is not.
Crediting Kenney is not required by CC0. It is here because it should be.
What is not in it
Named honestly rather than left to be discovered:
- No music under the game, only event sounds and two four-note stings. There is room in the third voice for it; there was not much room anywhere else when it was written. The conversion gave some of that room back — the variable table is under the 128 ceiling with a handful to spare and the label table is at 57 of 64, where it was at 61.
- One gem at a time. There is one sprite slot for it. A brick broken while a gem is falling drops nothing.
- Sticky and multiball share one offset. Two balls stuck to the paddle at once sit on top of each other. It is rare enough that fixing it would cost a variable I do not have.
- No high score on disk. There is no disk.
- No attract mode, unlike
../characters. It sits on the title screen until somebody presses space, which also means it cannot test itself unattended the way that one can.
The eight interpreter defects this game turned up are filed in TODO.md §9, each with a
reduction that fits on a screen and the file and line of the cause. Six are now fixed
— the leaking DEF call, the skipped block that broke its caller's RETURN, the ignored
subscript on SSHAPE, GRAPHIC CLR, a negative DATA item, and half of the invisible
drawing. The two that stand are the left-operand arithmetic rule, which turned out to be a
decision rather than a defect and is now documented as one, and the 256-line batch tear,
which belongs to the host.
The listing has since been converted, and its header records what went. It used to
spend two of its eight sprites on the screen itself — an SSHAPE of the HUD strip and one
of the whole play field, because a drawing lasted a single frame and a sprite was the only
thing redrawn for nothing. A drawing persists now, so both slots are free, the PACE
routine that hunted for a frame boundary is gone with the captures it protected, and the
flattened live list that made a full-field redraw cheap is gone with the redraw itself: a
broken brick is erased in place.
What has not changed is the shape of the workarounds that no longer cost anything — six
separate scalars for six brick stamps, loops guarded by GOTO rather than wrapped in a
block. Its comments say which of the five traps still stand and which are marked FIXED.