`HITTEST`, `XBRICK` and `YBRICK` are gone -- about forty lines that divided
pixels by cell sizes to recover a grid index, tested the ball's leading edge
rather than its box, and could miss a brick clipped at the corner by seven
pixels' worth of ball. In their place: sixty `SOLID` rectangles registered as the
wall is built, `COLLISION 2, BRICKHIT`, and a fifteen-line handler.
The handler reads better than what it replaces because it asks rather than
derives. `RCOLLISION(1, 1)` is which brick -- the id is the array index plus one,
so nothing is looked up. Fields 2, 3 and 4 are the way out and how far, so the
ball is pushed exactly clear instead of being restored to a remembered `OX#`/`OY#`.
Field 7 is which axis to reverse, which `TESTCELL` in the other game computes by
hand from an overlap rectangle.
`MOVEBAL` loses its two brick calls and its position backup. `KILLBR` retires the
rectangle in the same breath as clearing the array element, so the next frame
cannot hit a brick that is no longer drawn.
**A latent defect in the target prescan had to be fixed first, and `RCOLLISION`
is the first name in the language to reach it.** `src/renumber.c` walks a line
character by character looking for `GOTO`, `GOSUB`, `COLLISION` and the rest, and
checked only the character *after* a match -- so `RCOLLISION(1, 1)` found
`COLLISION` at its second character, read the `(1,` that followed as a handler
line number, and refused the whole program with "branch to line 1, which the
program did not number", naming a line that contains no branch at all. It now
requires a word boundary on both sides. The comment there was already right that
the trailing check protects `GOTOX#`; nothing protected `XGOTO#`.
`tests/unnumbered.c` covers all three shapes and TODO.md section 6 item 42
records it.
The game runs ninety seconds headless with no error line and the attract mode
scores 1320, so bricks are being found and broken through the new path.
Chapter 17 is not updated yet -- that is the other half of section 6 item 39, and
it is a bigger edit than this one.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL
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>
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>
