Add two Breakout examples and the tutorials that build them
Two complete games in `examples/breakout/`, both 100% BASIC: `characters/`
draws its wall in the text grid with two `DATA` sprites for the ball and
paddle, and `sprites/` loads CC0 artwork and captures its whole screen with
`SSHAPE`/`SPRSAV`. They take opposite shapes for reasons that are entirely
this interpreter's, which is what the chapters are for.
`docs/17-tutorial-breakout.md` and `docs/18-tutorial-breakout-artwork.md`
build each one a step at a time, and end in a checklist of the rules a real
program runs into: create every name before the loop starts, write a text row
whole, loop with `GOTO` rather than `DO`, put the float on the left. Every
trap is a runnable block with its own output rather than a claim -- the value
pool dying at four thousand names, the skipped `BEGIN` block that breaks its
caller's `RETURN`, `SSHAPE` ignoring a subscript, `READ`'s single cursor.
Five figures, generated from the listings beside them by `docs_screenshots`,
and a `breakout_art` setup so the ones that load artwork load the example's
own. The character game's wall cannot be photographed -- the screenshot host
omits the text layer on purpose -- so it is shown as compared output instead.
`docs/07-sound.md` never said `SOUND`'s frequency is a SID register value
rather than hertz, which both games depend on. It says so now, with the
conversion from `src/audio_tables.c:84`.
`TODO.md` gains the thirteen defects the two games turned up -- §6 items 30
to 33 and all of §9 -- each with a reduction that fits on a screen, the file
and line of the cause, and what a fix would touch.
Verified: `docs_examples` passes in both build configurations,
`docs_screenshots --check` re-renders all thirteen figures and byte-compares
them, the full 109-test suite passes in both builds, every quoted fragment
was checked to appear verbatim in the listing it came from, and every
relative link and anchor resolves.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 22:54:42 -04:00
|
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# Breakout
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Breakout, written entirely in BASIC for the AKGL BASIC interpreter. The ball and the
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paddle are sprites defined from `DATA` in the listing; the bricks, the HUD and the
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messages are characters in the text grid.
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```sh
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../../../build-akgl/basic breakout.bas
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```
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|
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|
Stop the listings and their chapters stating fixed defects as fact
You were right that this was still everywhere. The two `.bas` files carried
their workarounds as present-tense statements about the interpreter -- "a name
first created inside a GOSUB costs a value slot that is never handed back",
"writing PAST the terminator of a short row draws nothing at all", "SSHAPE and
GSHAPE ignore the subscript on a string array", "a FOR inside a BEGIN block does
not survive the RETURN" -- and every one of those is now false. A comment that
lies is worse than no comment, and these were the first thing anybody opening
the files would read.
**The characters game takes the geometry fix.** `CW# = 16` becomes `CW# =
RGR(3)`, and the grid comes from `RWINDOW`, so the game fits whatever window and
font the host gives it. That was the one thing in the listing that would break on
a different font, and `RGR(3)` and `RWINDOW` were added to the interpreter
because of it -- leaving the constant in place while Chapter 17 teaches the
function was the inconsistency worth closing. `RGR(1)` still comes first so a
build with no graphics device refuses by naming the device that is missing.
Everything else in both listings keeps its shape and says why. Declaring every
name up front, guarding loops with `GOTO`, six scalars for six brick stamps: none
is forced any more and none costs anything, so they stay, with the comments
marking which rules stand and which are history. The sprites header's five traps
are marked FIXED where they are fixed.
The chapters follow: Chapter 17 Step 2 no longer says "the listing still has
`CW# = 16`", and Chapter 18's trap section is "five things that did not do what
they looked like" with the two that still stand named up front rather than left
to be counted.
Verified: Chapter 17 Step 2's block is once again verbatim from the listing, so
every quoted fragment in both chapters matches its source with no exceptions;
both games run 40 seconds on the SDL frontend with no error line; both suites
green in both configurations; `docs_examples` and `docs_screenshots --check`
pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-02 06:32:48 -04:00
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It needs the SDL build. The stdio build has no graphics device, so the first `RGR` refuses
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and the game stops there — which is exactly what it should do.
|
Add two Breakout examples and the tutorials that build them
Two complete games in `examples/breakout/`, both 100% BASIC: `characters/`
draws its wall in the text grid with two `DATA` sprites for the ball and
paddle, and `sprites/` loads CC0 artwork and captures its whole screen with
`SSHAPE`/`SPRSAV`. They take opposite shapes for reasons that are entirely
this interpreter's, which is what the chapters are for.
`docs/17-tutorial-breakout.md` and `docs/18-tutorial-breakout-artwork.md`
build each one a step at a time, and end in a checklist of the rules a real
program runs into: create every name before the loop starts, write a text row
whole, loop with `GOTO` rather than `DO`, put the float on the left. Every
trap is a runnable block with its own output rather than a claim -- the value
pool dying at four thousand names, the skipped `BEGIN` block that breaks its
caller's `RETURN`, `SSHAPE` ignoring a subscript, `READ`'s single cursor.
Five figures, generated from the listings beside them by `docs_screenshots`,
and a `breakout_art` setup so the ones that load artwork load the example's
own. The character game's wall cannot be photographed -- the screenshot host
omits the text layer on purpose -- so it is shown as compared output instead.
`docs/07-sound.md` never said `SOUND`'s frequency is a SID register value
rather than hertz, which both games depend on. It says so now, with the
conversion from `src/audio_tables.c:84`.
`TODO.md` gains the thirteen defects the two games turned up -- §6 items 30
to 33 and all of §9 -- each with a reduction that fits on a screen, the file
and line of the cause, and what a fix would touch.
Verified: `docs_examples` passes in both build configurations,
`docs_screenshots --check` re-renders all thirteen figures and byte-compares
them, the full 109-test suite passes in both builds, every quoted fragment
was checked to appear verbatim in the listing it came from, and every
relative link and anchor resolves.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 22:54:42 -04:00
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| Key | Does |
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|---|---|
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| left / right | move the paddle |
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| space | start a game from the title screen, then launch the ball |
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| P | pause |
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| Q or escape | quit |
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The title screen plays itself. Attract mode is a real feature and it is also how the game
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was tested without a hand on the keyboard.
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Three lives, six rows of bricks worth 60 down to 10 points a row, three level layouts that
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repeat with a faster ball each time, and a high score that lasts as long as the process
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does.
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## How it works, and how to write your own
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Rewrite the two game tutorials as instructions rather than commentary
Chapters 17 and 18 read as a code review of a finished listing: they explained
why each decision had been made, walked through the project's own history, and
led with what had once been broken. A reader who wanted to build the game got
the reasoning and had to reconstruct the program.
Both are now step-by-step. Each opens with a picture of the finished game and a
bullet list of the steps, each bullet is a section, and each section states its
goal, shows the code, and says how to check it. Chapter 17 is sixteen steps and
Chapter 18 is thirteen, and the last of each is the assembly: the order of the
file, the full declaration block, and the routines the earlier steps referred to.
Project history is gone -- it belongs in Chapter 14 and in git -- and where a
listing has to do something awkward, the tutorial shows how first and names the
`TODO.md` item that will make it unnecessary second.
**Three defects had no entry anywhere**, which the rewrite found by trying to
state each rule as a rule. §6 item 35: `a - b + c` computes `a - (b + c)`,
because `subtraction()` sits above `addition()` as its own precedence level and
the inner loop eats the `+`. Item 36: only one unparenthesised `AND` or `OR` is
matched, which is item 12's `if`-where-`while` on the one operator pair item 12
did not reach. Item 37: a `GOTO` out of a `FOR` or a `DO` leaks the loop's scope,
so a main loop written that way stops on the thirty-second lost life -- which is
why both games are built out of `LABEL` and `GOTO`, and it is a workaround rather
than a preference. Chapter 3 gains the identifier rule the third trial ran into:
there is no underscore in a name, and the error says `UNKNOWN TOKEN _`.
**`tools/screenshot.c` learned to draw the text layer**, behind a new `text=1`
fence attribute, because Chapter 17's game is characters in the grid and a figure
without that layer is two sprites on black. It opens the bundled font at the size
the standalone frontend uses, so a figure's cell size is the reader's cell size,
and it uses the akgl sink alone rather than a tee so the program's output lands in
the picture instead of on the stdout the caller reads to decide a figure failed.
Both new figures -- `breakout-game.png` and `breakout-game-artwork.png` -- are
generated from listings in the chapters like every other one.
Verified by handing each chapter, alone, to an agent on a much smaller model and
telling it to build the game from the tutorial text with the `examples/` tree off
limits. The first pass scored 3.5 and 3 out of 10 and named what was missing:
routines referred to but never shown, the third level layout, the sprite `DATA`,
the font table, edits to earlier routines that were never marked as edits. Those
are now in. The second pass built a 658-line Chapter 17 game that plays itself
for ninety seconds with the score at 1890 and no error line, and the third built
a 1053-line Chapter 18 game with 61 labels, no invented routines, no gaps found,
and forty seconds clean. 9/10 and 8/10.
One real bug in the new prose, caught in review: Chapter 18's `HITBAR` did not
set the `HIT#` that `BALLPADDLE` reads to decide whether the paddle already
caught the ball. Both suites green in both configurations, `docs_examples` and
`docs_screenshots --check` pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL
2026-08-02 08:08:23 -04:00
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|
**[Chapter 17 of the guide](../../../docs/17-tutorial-breakout.md)** builds this program in
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fifteen steps you can type in one at a time, starting from an empty file: measuring the
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screen, declaring every name before anything uses it, making the two sprites out of `DATA`,
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|
building a text row whole, the main loop, the ball, the bounce, and the attract mode. It is
|
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|
the tutorial; this is the finished thing.
|
Add two Breakout examples and the tutorials that build them
Two complete games in `examples/breakout/`, both 100% BASIC: `characters/`
draws its wall in the text grid with two `DATA` sprites for the ball and
paddle, and `sprites/` loads CC0 artwork and captures its whole screen with
`SSHAPE`/`SPRSAV`. They take opposite shapes for reasons that are entirely
this interpreter's, which is what the chapters are for.
`docs/17-tutorial-breakout.md` and `docs/18-tutorial-breakout-artwork.md`
build each one a step at a time, and end in a checklist of the rules a real
program runs into: create every name before the loop starts, write a text row
whole, loop with `GOTO` rather than `DO`, put the float on the left. Every
trap is a runnable block with its own output rather than a claim -- the value
pool dying at four thousand names, the skipped `BEGIN` block that breaks its
caller's `RETURN`, `SSHAPE` ignoring a subscript, `READ`'s single cursor.
Five figures, generated from the listings beside them by `docs_screenshots`,
and a `breakout_art` setup so the ones that load artwork load the example's
own. The character game's wall cannot be photographed -- the screenshot host
omits the text layer on purpose -- so it is shown as compared output instead.
`docs/07-sound.md` never said `SOUND`'s frequency is a SID register value
rather than hertz, which both games depend on. It says so now, with the
conversion from `src/audio_tables.c:84`.
`TODO.md` gains the thirteen defects the two games turned up -- §6 items 30
to 33 and all of §9 -- each with a reduction that fits on a screen, the file
and line of the cause, and what a fix would touch.
Verified: `docs_examples` passes in both build configurations,
`docs_screenshots --check` re-renders all thirteen figures and byte-compares
them, the full 109-test suite passes in both builds, every quoted fragment
was checked to appear verbatim in the listing it came from, and every
relative link and anchor resolves.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 22:54:42 -04:00
|
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|
[Chapter 18](../../../docs/18-tutorial-breakout-artwork.md) does the same for
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[`../sprites`](../sprites), which builds the same game out of loaded artwork and comes out
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a completely different program.
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## Known warts, this game's own
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|
|
|
|
Stop the listings and their chapters stating fixed defects as fact
You were right that this was still everywhere. The two `.bas` files carried
their workarounds as present-tense statements about the interpreter -- "a name
first created inside a GOSUB costs a value slot that is never handed back",
"writing PAST the terminator of a short row draws nothing at all", "SSHAPE and
GSHAPE ignore the subscript on a string array", "a FOR inside a BEGIN block does
not survive the RETURN" -- and every one of those is now false. A comment that
lies is worse than no comment, and these were the first thing anybody opening
the files would read.
**The characters game takes the geometry fix.** `CW# = 16` becomes `CW# =
RGR(3)`, and the grid comes from `RWINDOW`, so the game fits whatever window and
font the host gives it. That was the one thing in the listing that would break on
a different font, and `RGR(3)` and `RWINDOW` were added to the interpreter
because of it -- leaving the constant in place while Chapter 17 teaches the
function was the inconsistency worth closing. `RGR(1)` still comes first so a
build with no graphics device refuses by naming the device that is missing.
Everything else in both listings keeps its shape and says why. Declaring every
name up front, guarding loops with `GOTO`, six scalars for six brick stamps: none
is forced any more and none costs anything, so they stay, with the comments
marking which rules stand and which are history. The sprites header's five traps
are marked FIXED where they are fixed.
The chapters follow: Chapter 17 Step 2 no longer says "the listing still has
`CW# = 16`", and Chapter 18's trap section is "five things that did not do what
they looked like" with the two that still stand named up front rather than left
to be counted.
Verified: Chapter 17 Step 2's block is once again verbatim from the listing, so
every quoted fragment in both chapters matches its source with no exceptions;
both games run 40 seconds on the SDL frontend with no error line; both suites
green in both configurations; `docs_examples` and `docs_screenshots --check`
pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-02 06:32:48 -04:00
|
|
|
- **The cell size used to be a constant.** `CW#` and `CH#` were 16, measured by hand
|
|
|
|
|
against the bundled C64_Pro_Mono at 16 points, because BASIC had no way to ask — and it
|
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|
|
|
was the one thing here that would break on a different font. `RGR(3)`, `RGR(4)` and
|
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|
|
|
`RWINDOW` were added to the interpreter because of this listing, and it uses them now,
|
|
|
|
|
so the game fits whatever window and font the host gives it.
|
Add two Breakout examples and the tutorials that build them
Two complete games in `examples/breakout/`, both 100% BASIC: `characters/`
draws its wall in the text grid with two `DATA` sprites for the ball and
paddle, and `sprites/` loads CC0 artwork and captures its whole screen with
`SSHAPE`/`SPRSAV`. They take opposite shapes for reasons that are entirely
this interpreter's, which is what the chapters are for.
`docs/17-tutorial-breakout.md` and `docs/18-tutorial-breakout-artwork.md`
build each one a step at a time, and end in a checklist of the rules a real
program runs into: create every name before the loop starts, write a text row
whole, loop with `GOTO` rather than `DO`, put the float on the left. Every
trap is a runnable block with its own output rather than a claim -- the value
pool dying at four thousand names, the skipped `BEGIN` block that breaks its
caller's `RETURN`, `SSHAPE` ignoring a subscript, `READ`'s single cursor.
Five figures, generated from the listings beside them by `docs_screenshots`,
and a `breakout_art` setup so the ones that load artwork load the example's
own. The character game's wall cannot be photographed -- the screenshot host
omits the text layer on purpose -- so it is shown as compared output instead.
`docs/07-sound.md` never said `SOUND`'s frequency is a SID register value
rather than hertz, which both games depend on. It says so now, with the
conversion from `src/audio_tables.c:84`.
`TODO.md` gains the thirteen defects the two games turned up -- §6 items 30
to 33 and all of §9 -- each with a reduction that fits on a screen, the file
and line of the cause, and what a fix would touch.
Verified: `docs_examples` passes in both build configurations,
`docs_screenshots --check` re-renders all thirteen figures and byte-compares
them, the full 109-test suite passes in both builds, every quoted fragment
was checked to appear verbatim in the listing it came from, and every
relative link and anchor resolves.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 22:54:42 -04:00
|
|
|
- **Every character the game draws also goes to stdout**, because the frontend tees the
|
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|
|
text sink to the terminal. It made the whole game auditable from a log file during
|
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|
development and it is pure noise the rest of the time. Redirect it.
|
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|
|
- **Collision is against the cell the ball's leading edge is in**, so a brick clipped at
|
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|
|
the very corner can be missed by up to seven pixels' worth of ball. Testing the centre
|
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|
|
instead was worse: the ball sank four pixels into a brick before it turned.
|
|
|
|
|
- **There is a stall watchdog.** Ten seconds without touching a brick and the ball gets a
|
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|
|
new angle — at the *next paddle bounce*, never in mid-air.
|
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|
|
- **The demo cannot lose**, it re-serves. It also cannot be paused; `P` is ignored until a
|
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|
|
real game starts.
|
|
|
|
|
- **Sound is asked for once and then believed.** On a machine with no audio device the
|
|
|
|
|
game is silent rather than dead.
|
|
|
|
|
- **No high score on disk.** There is no disk in this interpreter.
|
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|
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|
|
Bring the tutorials back in line with the fixed interpreter
Eleven of the thirteen defects these two games found are fixed, and the
chapters that taught around them said things that are no longer true.
Chapter 17: the drawing verbs are no longer invisible, they are covered by a
text layer that `WINDOW` can now shrink; the cell size is `RGR(3)` and the grid
is `RWINDOW`, not a hand-measured constant; a character written past a short
row's end lands. Chapter 18: traps 3 and 4 -- the skipped block that broke its
caller's `RETURN`, and `SSHAPE` ignoring a subscript -- become history rather
than warnings, and Step 3 no longer claims a sprite is the *only* way to put a
picture up, only the one that costs nothing.
**Neither `.bas` listing changes, and both READMEs now say why.** The character
game still writes `CW# = 16` and the artwork game still keeps six brick stamps
in six scalars. What those listings are worth is being what a program written
against those constraints looks like, with comments explaining what each one was
avoiding -- rewriting them to pretend the problems never existed would throw
that away. So Chapter 17 Step 2 shows the `RGR(3)`/`RWINDOW` form and says
plainly that the listing beside it does not use it. That is the one place in
either chapter where a quoted fragment is not verbatim from the game.
Also: the closing pointers now say which entries are struck and which stand, and
the budgets table in Chapter 18 notes that several of those budgets were tighter
when the game was written.
TODO.md section 9 item 3 is updated rather than struck: the `WINDOW` half is
fixed, the default text area owning the whole window is not, and whether that
default is right is a question rather than a defect.
Verified against the fixed interpreter: both games run 45 seconds on the SDL
frontend with no error line and the score climbing; both suites are green in
both configurations; `docs_examples` passes and `docs_screenshots --check`
re-renders all thirteen figures byte-identically; coverage is 95.0% of lines
against the 90 gate, with src/variable.c at 100%; and every other quoted
fragment still appears verbatim in the listing it came from.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-02 00:31:06 -04:00
|
|
|
The interpreter defects this game turned up are filed in `TODO.md` §6 and §9, each with a
|
|
|
|
|
reduction that fits on a screen. Most are now fixed — the value pool that killed the first
|
|
|
|
|
version after twenty-five seconds, the unreachable `WINDOW`, the character written past a
|
|
|
|
|
short row — and the entries are struck rather than deleted, because the reduction is worth
|
Stop the listings and their chapters stating fixed defects as fact
You were right that this was still everywhere. The two `.bas` files carried
their workarounds as present-tense statements about the interpreter -- "a name
first created inside a GOSUB costs a value slot that is never handed back",
"writing PAST the terminator of a short row draws nothing at all", "SSHAPE and
GSHAPE ignore the subscript on a string array", "a FOR inside a BEGIN block does
not survive the RETURN" -- and every one of those is now false. A comment that
lies is worse than no comment, and these were the first thing anybody opening
the files would read.
**The characters game takes the geometry fix.** `CW# = 16` becomes `CW# =
RGR(3)`, and the grid comes from `RWINDOW`, so the game fits whatever window and
font the host gives it. That was the one thing in the listing that would break on
a different font, and `RGR(3)` and `RWINDOW` were added to the interpreter
because of it -- leaving the constant in place while Chapter 17 teaches the
function was the inconsistency worth closing. `RGR(1)` still comes first so a
build with no graphics device refuses by naming the device that is missing.
Everything else in both listings keeps its shape and says why. Declaring every
name up front, guarding loops with `GOTO`, six scalars for six brick stamps: none
is forced any more and none costs anything, so they stay, with the comments
marking which rules stand and which are history. The sprites header's five traps
are marked FIXED where they are fixed.
The chapters follow: Chapter 17 Step 2 no longer says "the listing still has
`CW# = 16`", and Chapter 18's trap section is "five things that did not do what
they looked like" with the two that still stand named up front rather than left
to be counted.
Verified: Chapter 17 Step 2's block is once again verbatim from the listing, so
every quoted fragment in both chapters matches its source with no exceptions;
both games run 40 seconds on the SDL frontend with no error line; both suites
green in both configurations; `docs_examples` and `docs_screenshots --check`
pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-02 06:32:48 -04:00
|
|
|
keeping.
|
|
|
|
|
|
|
|
|
|
**The listing takes the geometry fix and leaves the rest of its shape alone.** Measuring
|
|
|
|
|
the cell instead of assuming it makes the game strictly better, so it does. Declaring
|
|
|
|
|
every name up front and looping with `GOTO` are no longer forced by anything, and are
|
|
|
|
|
still what the file does — its comments now say which rules stand and which are history.
|
Add two Breakout examples and the tutorials that build them
Two complete games in `examples/breakout/`, both 100% BASIC: `characters/`
draws its wall in the text grid with two `DATA` sprites for the ball and
paddle, and `sprites/` loads CC0 artwork and captures its whole screen with
`SSHAPE`/`SPRSAV`. They take opposite shapes for reasons that are entirely
this interpreter's, which is what the chapters are for.
`docs/17-tutorial-breakout.md` and `docs/18-tutorial-breakout-artwork.md`
build each one a step at a time, and end in a checklist of the rules a real
program runs into: create every name before the loop starts, write a text row
whole, loop with `GOTO` rather than `DO`, put the float on the left. Every
trap is a runnable block with its own output rather than a claim -- the value
pool dying at four thousand names, the skipped `BEGIN` block that breaks its
caller's `RETURN`, `SSHAPE` ignoring a subscript, `READ`'s single cursor.
Five figures, generated from the listings beside them by `docs_screenshots`,
and a `breakout_art` setup so the ones that load artwork load the example's
own. The character game's wall cannot be photographed -- the screenshot host
omits the text layer on purpose -- so it is shown as compared output instead.
`docs/07-sound.md` never said `SOUND`'s frequency is a SID register value
rather than hertz, which both games depend on. It says so now, with the
conversion from `src/audio_tables.c:84`.
`TODO.md` gains the thirteen defects the two games turned up -- §6 items 30
to 33 and all of §9 -- each with a reduction that fits on a screen, the file
and line of the cause, and what a fix would touch.
Verified: `docs_examples` passes in both build configurations,
`docs_screenshots --check` re-renders all thirteen figures and byte-compares
them, the full 109-test suite passes in both builds, every quoted fragment
was checked to appear verbatim in the listing it came from, and every
relative link and anchor resolves.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-01 22:54:42 -04:00
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## How this was checked
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- Parses clean under the stdio `basic` (it then stops at the first graphics verb, as it
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should).
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- Attract mode run for 145 seconds and again for 110: no runtime error, score climbing
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throughout, 39 bricks in the second run.
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- Level clear verified against a copy whose first layout is a single row: `LEVEL CLEARED`,
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layout 2 loaded, ball speed up, play continues.
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- Input driven with `xdotool` against the real window: paddle moves and clamps at both
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edges, ball launches, `P` pauses and unpauses, three lives drain to `GAME OVER`, space
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starts a new game, `Q` exits printing the final and high scores.
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- Every direction change logged for a whole run and read back: each one is a wall, a brick
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or the paddle. Nothing turns without a reason.
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