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>
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>
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>
