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>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-01 22:54:42 -04:00
# 18. Tutorial: Breakout with artwork
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
This chapter builds Breakout a second time, out of loaded PNG artwork, with a drawn
brick field, five powerups, three voices of sound and a HUD in colour. It is a bigger
program than [Chapter 17 ](17-tutorial-breakout.md )'s and it uses a completely different set
of verbs: everything here is drawn or loaded, and nothing is written into the text grid.
This is what you are building:
The finished listing is
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>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-01 22:54:42 -04:00
[`examples/breakout/sprites/breakout.bas` ](../examples/breakout/sprites/breakout.bas ).
Read Chapter 17 first if you have not. The rules it teaches — declare every name up front,
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
loop with `GOTO` , parenthesise mixed `+` and `-` , build a random-number generator — all
apply here too, and are not repeated.
One of them is worth repeating, because this chapter leans on it harder than Chapter 17
does. * * `#` is an integer, `%` is a float and `$` is a string.** That is the opposite way
round from Commodore BASIC, and it is why ball positions and velocities here are `BLX%` and
`BLVX%` while counters and flags are `BLN#` and `BLON#` . Get one wrong and the ball moves in
whole pixels, or stops.
[Chapter 3 ](03-the-language.md ) is the language reference for the rest — `MOD` , `INSTR` ,
`MID` , `LEN` — and [Chapter 4 ](04-control-flow.md ) is `BEGIN` /`BEND` , `DO ... LOOP UNTIL`
and `GOSUB` .
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>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-01 22:54:42 -04:00
```sh norun
$ ./build-akgl/basic examples/breakout/sprites/breakout.bas
```
| 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 |
A broken brick drops a gem about one time in seven. Catch it with the paddle; the colour
tells you which it is.
| 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 |
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
## What you will do
- **[Step 1 ](#step-1-put-artwork-on-the-screen )** — load PNG artwork into sprites
- **[Step 2 ](#step-2-budget-the-eight-sprite-slots )** — decide what each of the eight
sprites is, before writing anything else
2026-08-02 13:13:51 -04:00
- **[Step 3 ](#step-3-make-room-for-what-you-draw )** — take the text layer out of the way,
so what you draw can be seen and stays seen
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
- **[Step 4 ](#step-4-make-the-brick-stamps )** — make one brick per colour and stamp the
field out of them
2026-08-02 13:13:51 -04:00
- **[Step 5 ](#step-5-draw-at-most-one-thing-per-frame )** — draw at most one thing per
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
frame, chosen by dirty flags
2026-08-02 13:13:51 -04:00
- **[Step 6 ](#step-6-erase-one-brick-not-the-whole-field )** — erase a broken brick in
place, so the field is drawn once and not rebuilt
- **[Step 7 ](#step-7-draw-lettering-with-a-stroke-font )** — draw lettering with a stroke
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
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
2026-08-02 08:08:23 -04:00
font, because text has no colour
