Fix 80-column fixtures and tutorial expectations

AKBASIC_MAX_LINE_LENGTH's cut from 256 to 80 left seventeen lines of
examples/megademo unloadable: the sixteen IM$() picture strings (up to
252 characters) and TUNEA/TUNEB's four-bar PLAY strings (174 and 175).
The real ceiling is 78 characters, not 80 -- stdio_readline() refuses a
read that fills the 80-byte buffer without a newline, so content plus
its terminator must fit in 79.

The picture: vaporwave.py's PAYLOAD drops from 240 to 64, so every
emitted IM$(NN) = "..." line fits under the ceiling. chop() no longer
slices blind; it walks the stream a record at a time -- two characters
for a run, three for an R row record -- and never cuts inside one,
because the decoder reads a record's tail with MID on the string it is
walking and a record straddling two IM$ entries decodes as garbage.
The old blind slice at 240 only happened to be safe. verify() now
simulates the CHOPPED strings with the cursor threaded across the
boundaries exactly the way DRAWSTREAM executes them, so a bad cut is
an assertion failure instead of a corrupted screen, and emit_block()
asserts every emitted line fits. The picture is 56 strings where it
was 16; the decoder needed no changes at all, since it already carries
X#/Y# from one IM$ entry to the next.

The music: TUNEA and TUNEB each become four PLAY statements, one bar
apiece. play.c keeps voice, envelope, level and duration state on the
runtime across statements and every PLAY appends to the same queue, so
four bars queue exactly as one long string did. Each bar restates the
V1T3U9S prefix so a bar dropped by QFULL cannot leave the next batch
playing on the drum kit's envelope.

Everything still clears the shrunken pools with room to spare: 1625
source lines of 2048, ~704 array slots of 2048, identifiers within the
24-character symtab key. Verified end to end against this branch's
build: the demo loads, the offscreen host renders every scene, and the
scene-5 still is pixel-identical to vaporwave.py's own preview. The
test suite fails the same seventeen cases with and without this
commit.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ACffnV6F7sxQuG3Y8a1L3s

docs/17-tutorial-breakout.md

@@ -685,9 +685,9 @@ seconds asks for fifty frames a second.
 ### Why `GOTO` rather than `DO ... LOOP`
 
 A `DO ... LOOP` around the frame would read better, and it is not usable here: **a `GOTO`
-that jumps out of a `FOR` or a `DO` does not release the loop's scope.** There are 32
+that jumps out of a `FOR` or a `DO` does not release the loop's scope.** There are 12
 scopes, so a game that leaves its main loop once per lost life stops on the
-thirty-second one:
+twelfth one:
 
 ```basic
 N# = 0
@@ -700,7 +700,7 @@ PRINT "SURVIVED " + N#
 ```
 
 ```output
-? 3 : PARSE ERROR Environment pool exhausted at line 3 (32 in use)
+? 3 : PARSE ERROR Environment pool exhausted at line 3 (12 in use)
 
 ```
 

docs/18-tutorial-breakout-artwork.md

@@ -1423,7 +1423,8 @@ IF STATE# = 2 THEN GOSUB UNSTICK
 RETURN
 
 LABEL PRESSPAUSE
-IF STATE# = 2 THEN STATE# = 6 : GMTYP# = 0 : BAN$ = "PAUSED" : GOSUB SETBANNER : RETURN
+IF STATE# = 2 THEN STATE# = 6 : GMTYP# = 0 : BAN$ = "PAUSED"
+IF STATE# = 6 THEN GOSUB SETBANNER : RETURN
 IF STATE# = 6 THEN STATE# = 2 : BAN$ = "" : GOSUB SETBANNER
 RETURN
 ```

examples/megademo/README.md

@@ -56,7 +56,10 @@ This is a tour of the interpreter's edges, on purpose:
   counterpoint: a genuine 24x21 `SPRSAV` type-in sprite, 63 bytes, which is
   everything `DATA` has room to say. The paint is the reveal, and the exit is a
   stride-63 column dissolve — 63 is coprime to 160, so the walk hits every
-  column once and looks random while carrying no state.
+  column once and looks random while carrying no state. The strings come in
+  64-character chunks because a source line is 80 columns, like the machines
+  this pretends to be — the decoder carries its cursor from one `IM$` entry to
+  the next, and the generator refuses to cut inside a run.
 - **And then the picture is video.** Six delta frames loop the floor grid toward
   you and crawl the sun's slice pattern — full motion video, 1.3 KB total, about
   220 bytes a frame. A delta re-encodes only the rows that changed: an `R`
@@ -82,6 +85,10 @@ This is a tour of the interpreter's edges, on purpose:
   batch a bar of noise drums. Noise is real: `ENVELOPE`'s sixth argument is a
   waveform, 0 to 3, which Chapter 7 forgot to mention. Voice 1 carries the tune so
   the collision blips (voice 2) and scene sweeps (voice 3) never steal its channel.
+  A batch is four `PLAY` statements, one bar each — the 80-column line limit will
+  not hold four bars in one string, and it does not need to: the parser's voice,
+  envelope and duration state persists across statements and every `PLAY` appends
+  to the same queue, so four bars queue exactly as one line would.
 
 It also probes for its hardware like a proper boot loader, with one `TRAP` per
 device: no graphics refuses by name and exits, no audio mutes the soundtrack, no

examples/megademo/megademo.bas

@@ -461,38 +461,78 @@ BS% = W# / 160
 IF BS% < 1 THEN BS% = 1
 REM  ---- PICTURE-BEGIN (generated by vaporwave.py; do not
 REM  ---- hand-edit -- rerun the script to change the picture)
-DIM IM$(16)
+DIM IM$(56)
 DIM VA#(6)
 DIM VB#(6)
-NS# = 9
-VA#(0) = 9
-VB#(0) = 9
-VA#(1) = 10
-VB#(1) = 10
-VA#(2) = 11
-VB#(2) = 12
-VA#(3) = 13
-VB#(3) = 13
-VA#(4) = 14
-VB#(4) = 14
-VA#(5) = 15
-VB#(5) = 15
-IM$(0) = "G9G9G9G9GPGHEHG9GTEHG9GTEHGPGPEHG9GTEHG9GTEHGHGXEHGTBAG8EHG9GTEHG5EHGPEHG5EHGPEHG5EHGAPAG3EHGPEHG5EHGPEHGXGHEHG5EHGPEHG5EHGFBAGIEHGPGPEHGPEHGHEHGPEHGPEHGHEHGPEHGHEHGPEHGPEHGHEHGBPAGMEHGPEHGHEHGPEHGHEHGPEHGPEHGHEHGPEHGPEHGHEHGPEHGHEPGHEHGPEH"
-IM$(1) = "GHEPGHEHGPEHGHEPGHEHGHEGBAEHGHEHGPEHGHEPGHEHGPEHGHEHGPEHGHEPGHEHGPEHGHEPGHEHGPECPAEDGHEPGHEHGHEPGHEPGHEHGHEPGHEPGHEHGHEPGHEHGHEPGHEPGHECBAEDGHEPGHEPGHEHGHEPGHEHGHEPGHEPGHEHGHEPGHEPEPGHEPGHE5GHEPGHE5GHEHEXGHEPGHEEPAEZGHEPGHE5GHE5GHEPGHE5GHEP"
-IM$(2) = "GHE5GHE9ETGHE9ETGHEXEHGHE9ETGHHAE9ESGHEPEPGBBAGEE9EMHOE9ETGHEHE9E7HUE9E6E9E4H0E9E3E9E3H2E9EHBAETEHKHE9ELH6E9ECKHEPEPKHE9EBH9HAE9EIKHEHEXKHE2H9HCE9EPKHE5KHEPKDH9HEKCEPKHE5KHE5KHEKH9HGEBKHEPKHEXEHKHE5KHEBH9HIEIKHEPKHEPEPKHEPKHEHKAH9HKKHEHKHEP"
-IM$(3) = "KHEHKHEPKHEPKHH9HMEGKHEHKHEPKHEHKHEPKHEPH9HMEOKHEHKHEPKHEHKPEHKHEGH9HOKFEPKHEHKPEHKHEHKPEHKGH9HOEFKHEPKHEHKHEPKHEHKPEFH9HQKEEHKHEPKHEHKHEPKHEHKMH9HSKLEHKHEPKHEHKPEHKHEHKEH9HSEDKPEHKPEHKHEHKPEHKHEEH9HSKDEHKPEHKPKPEHKPEHKDH9HUECKHEHKPEHKHKXEH"
-IM$(4) = "KPEDH9HUKCEHK5EHK5EHKLH9HUKKEHK5EHK5EHKCH9HWEBKPEHKXKHEHK8I9IWKZEHKPKPEHK0I9IWK7EHKHKXEHKSI9IWK9KFEHK9KOI9IWK9KNK9KOI9IWK9KNK9KOI9IWK9KNKPIHKZI9IYK6IHKHKXIHKSI9IWK9KFIHK5IHKKI9IWK9KNIHK5IHKCI9IYKPIHKXKHIHK5IHKPIHK5IHKPIHKPKPIHK0I9IWKJIHKPIH"
-IM$(5) = "KHIHKPIHKPI9IZKBIHKHIHKPIHKHIHKPIHKKI9IWKJIHKHIHKPIHKHIHKPIHKDI9IXKPIHKHIHKHKHIHKHIPKHI9IYKCIHKPIHKHIHKPIHKHIPKHIHKPIHKHIPKHIHKPIHKHIHKPIHKHI9I9IHKHIHKPIHKHIPKHIHKHIEC9CSKDIPKHIPKHIHKHIPKHIHKEC9CSIDKHIPKHIPIPKHIPKHIFC9CQKEIHKHIPKHIHIXKHIPKG"
-IM$(6) = "C9COIFKHI5KHI5KHIPKHI5KHIPKHI5KHI5KHIPKHI5KHIPKHIXIHKHI9IDC9CMI4KHIPIPKHI6C9CKI9IDKHIHIXKHIZC9CII9IMKHI9IWC9CGI9IVI9I9I9I9IPI9I9I9I9IPQ9Q9Q9Q9QPE9E9E9E9EPE9E9E9E9EPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9"
-IM$(7) = "Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9"
-IM$(8) = "Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QP"
-IM$(9) = "RBRQ9QOKMQHK5RBSQ9QTI9IRRBXQ9QTKPQHKHQPKERBYQ9QPI9IHRB3Q9QSKAI5KHIJRB5Q9QTC9CMRB9Q9QWI9IGRCBQ9QYC9CCRCIA9A9A9A9APRCJE9E9E9E9EPRCNA9A9A9A9APRCOE9E9E9E9EPRCUA9A9A9A9APRCVE9E9E9E9EPRC5A9A9A9A9APRC7E9E9E9E9EP"
-IM$(10) = "RBQQ9QOK9KIQHKFRBRQ9QOI9IQRBWQ9QPKLQHKHQHKPRBXQ9QTI9QLIERB2Q9QRIBKHIPKHIPKCRB4Q9QSC9CORB8Q9QVI3KHIGRCAQ9QXC9CERCJA9A9A9A9APRCKE9E9E9E9EPRCOA9A9A9A9APRCPE9E9E9E9EPRCVA9A9A9A9APRCXE9E9E9E9EPRC7A9A9A9A9APRDAE9E9E9E9EP"
-IM$(11) = "RBPQ9QOK9KAQHKNRBQQ9QOI9IWRBVQ9QOKEQHKHQHKPQHKFRBWQ9QPI9IPRB1Q9QQKCIPKHIPKHIDRB3Q9QSC9CORB7Q9QUIWKHIPRB9Q9QWC9CGRCEA9A9A9A9APRCFE9E9E9E9EPRCGA9A9A9A9APRCHE9E9E9E9EPRCPA9A9A9A9APRCQE9E9E9E9EPRCXA9A9A9A9APRCZE9E9E9E9EPRDAA9A9A9A9APRDCE9E9E9E9"
-IM$(12) = "EP"
-IM$(13) = "RBOQ9QNK3QHKWRBPQ9QOI9IWRBUQ9QTKHQHKPQHKNRBVQ9QOI9IWRB0Q9QQIKKHIPKHIHKDRB1Q9QQC9CSRB2Q9QRC9CQRB6Q9QTIPKHIYRB8Q9QVC9CIRCKA9A9A9A9APRCLE9E9E9E9EPRCQA9A9A9A9APRCRE9E9E9E9EPRCZA9A9A9A9APRC1E9E9E9E9EPRDCA9A9A9A9APRDFE9E9E9E9EP"
-IM$(14) = "RBOQ9QNI9IYRBTQ9QOKEQHKPQHKVRBUQ9QTI9IRRBZQ9QTKHQHKPQHKHRB0Q9QQC9CSRB5Q9QTIHKHI5KARB7Q9QUC9CKRCBQ9QYI9ICRCHA9A9A9A9APRCIE9E9E9E9EPRCLA9A9A9A9APRCME9E9E9E9EPRCRA9A9A9A9APRCTE9E9E9E9EPRC1A9A9A9A9APRC3E9E9E9E9EPRDFA9A9A9A9APRDIE9E9E9E9EP"
-IM$(15) = "RBSQ9QTKPQHK3RBTQ9QOI9IWRBYQ9QPKDQHKPQHKHRBZQ9QTI9ILRB4Q9QSIAKHI5KHIBRB6Q9QTC9CMRCAQ9QXI9IERCEE9E9E9E9EPRCFA9A9A9A9APRCGE9E9E9E9EPRCMA9A9A9A9APRCNE9E9E9E9EPRCTA9A9A9A9APRCUE9E9E9E9EPRC3A9A9A9A9APRC5E9E9E9E9EPRDIA9A9A9A9AP"
+NS# = 32
+VA#(0) = 32
+VB#(0) = 35
+VA#(1) = 36
+VB#(1) = 39
+VA#(2) = 40
+VB#(2) = 43
+VA#(3) = 44
+VB#(3) = 47
+VA#(4) = 48
+VB#(4) = 51
+VA#(5) = 52
+VB#(5) = 55
+IM$(0) = "G9G9G9G9GPGHEHG9GTEHG9GTEHGPGPEHG9GTEHG9GTEHGHGXEHGTBAG8EHG9GTEH"
+IM$(1) = "G5EHGPEHG5EHGPEHG5EHGAPAG3EHGPEHG5EHGPEHGXGHEHG5EHGPEHG5EHGFBAGI"
+IM$(2) = "EHGPGPEHGPEHGHEHGPEHGPEHGHEHGPEHGHEHGPEHGPEHGHEHGBPAGMEHGPEHGHEH"
+IM$(3) = "GPEHGHEHGPEHGPEHGHEHGPEHGPEHGHEHGPEHGHEPGHEHGPEHGHEPGHEHGPEHGHEP"
+IM$(4) = "GHEHGHEGBAEHGHEHGPEHGHEPGHEHGPEHGHEHGPEHGHEPGHEHGPEHGHEPGHEHGPEC"
+IM$(5) = "PAEDGHEPGHEHGHEPGHEPGHEHGHEPGHEPGHEHGHEPGHEHGHEPGHEPGHECBAEDGHEP"
+IM$(6) = "GHEPGHEHGHEPGHEHGHEPGHEPGHEHGHEPGHEPEPGHEPGHE5GHEPGHE5GHEHEXGHEP"
+IM$(7) = "GHEEPAEZGHEPGHE5GHE5GHEPGHE5GHEPGHE5GHE9ETGHE9ETGHEXEHGHE9ETGHHA"
+IM$(8) = "E9ESGHEPEPGBBAGEE9EMHOE9ETGHEHE9E7HUE9E6E9E4H0E9E3E9E3H2E9EHBAET"
+IM$(9) = "EHKHE9ELH6E9ECKHEPEPKHE9EBH9HAE9EIKHEHEXKHE2H9HCE9EPKHE5KHEPKDH9"
+IM$(10) = "HEKCEPKHE5KHE5KHEKH9HGEBKHEPKHEXEHKHE5KHEBH9HIEIKHEPKHEPEPKHEPKH"
+IM$(11) = "EHKAH9HKKHEHKHEPKHEHKHEPKHEPKHH9HMEGKHEHKHEPKHEHKHEPKHEPH9HMEOKH"
+IM$(12) = "EHKHEPKHEHKPEHKHEGH9HOKFEPKHEHKPEHKHEHKPEHKGH9HOEFKHEPKHEHKHEPKH"
+IM$(13) = "EHKPEFH9HQKEEHKHEPKHEHKHEPKHEHKMH9HSKLEHKHEPKHEHKPEHKHEHKEH9HSED"
+IM$(14) = "KPEHKPEHKHEHKPEHKHEEH9HSKDEHKPEHKPKPEHKPEHKDH9HUECKHEHKPEHKHKXEH"
+IM$(15) = "KPEDH9HUKCEHK5EHK5EHKLH9HUKKEHK5EHK5EHKCH9HWEBKPEHKXKHEHK8I9IWKZ"
+IM$(16) = "EHKPKPEHK0I9IWK7EHKHKXEHKSI9IWK9KFEHK9KOI9IWK9KNK9KOI9IWK9KNK9KO"
+IM$(17) = "I9IWK9KNKPIHKZI9IYK6IHKHKXIHKSI9IWK9KFIHK5IHKKI9IWK9KNIHK5IHKCI9"
+IM$(18) = "IYKPIHKXKHIHK5IHKPIHK5IHKPIHKPKPIHK0I9IWKJIHKPIHKHIHKPIHKPI9IZKB"
+IM$(19) = "IHKHIHKPIHKHIHKPIHKKI9IWKJIHKHIHKPIHKHIHKPIHKDI9IXKPIHKHIHKHKHIH"
+IM$(20) = "KHIPKHI9IYKCIHKPIHKHIHKPIHKHIPKHIHKPIHKHIPKHIHKPIHKHIHKPIHKHI9I9"
+IM$(21) = "IHKHIHKPIHKHIPKHIHKHIEC9CSKDIPKHIPKHIHKHIPKHIHKEC9CSIDKHIPKHIPIP"
+IM$(22) = "KHIPKHIFC9CQKEIHKHIPKHIHIXKHIPKGC9COIFKHI5KHI5KHIPKHI5KHIPKHI5KH"
+IM$(23) = "I5KHIPKHI5KHIPKHIXIHKHI9IDC9CMI4KHIPIPKHI6C9CKI9IDKHIHIXKHIZC9CI"
+IM$(24) = "I9IMKHI9IWC9CGI9IVI9I9I9I9IPI9I9I9I9IPQ9Q9Q9Q9QPE9E9E9E9EPE9E9E9"
+IM$(25) = "E9EPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QP"
+IM$(26) = "Q9Q9Q9Q9QPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9"
+IM$(27) = "Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9"
+IM$(28) = "QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9"
+IM$(29) = "Q9Q9Q9QPE9E9E9E9EPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9"
+IM$(30) = "Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QP"
+IM$(31) = "Q9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QPQ9Q9Q9Q9QP"
+IM$(32) = "RBRQ9QOKMQHK5RBSQ9QTI9IRRBXQ9QTKPQHKHQPKERBYQ9QPI9IHRB3Q9QSKAI5"
+IM$(33) = "KHIJRB5Q9QTC9CMRB9Q9QWI9IGRCBQ9QYC9CCRCIA9A9A9A9APRCJE9E9E9E9EP"
+IM$(34) = "RCNA9A9A9A9APRCOE9E9E9E9EPRCUA9A9A9A9APRCVE9E9E9E9EPRC5A9A9A9A9"
+IM$(35) = "APRC7E9E9E9E9EP"
+IM$(36) = "RBQQ9QOK9KIQHKFRBRQ9QOI9IQRBWQ9QPKLQHKHQHKPRBXQ9QTI9QLIERB2Q9QR"
+IM$(37) = "IBKHIPKHIPKCRB4Q9QSC9CORB8Q9QVI3KHIGRCAQ9QXC9CERCJA9A9A9A9APRCK"
+IM$(38) = "E9E9E9E9EPRCOA9A9A9A9APRCPE9E9E9E9EPRCVA9A9A9A9APRCXE9E9E9E9EP"
+IM$(39) = "RC7A9A9A9A9APRDAE9E9E9E9EP"
+IM$(40) = "RBPQ9QOK9KAQHKNRBQQ9QOI9IWRBVQ9QOKEQHKHQHKPQHKFRBWQ9QPI9IPRB1Q9"
+IM$(41) = "QQKCIPKHIPKHIDRB3Q9QSC9CORB7Q9QUIWKHIPRB9Q9QWC9CGRCEA9A9A9A9AP"
+IM$(42) = "RCFE9E9E9E9EPRCGA9A9A9A9APRCHE9E9E9E9EPRCPA9A9A9A9APRCQE9E9E9E9"
+IM$(43) = "EPRCXA9A9A9A9APRCZE9E9E9E9EPRDAA9A9A9A9APRDCE9E9E9E9EP"
+IM$(44) = "RBOQ9QNK3QHKWRBPQ9QOI9IWRBUQ9QTKHQHKPQHKNRBVQ9QOI9IWRB0Q9QQIKKH"
+IM$(45) = "IPKHIHKDRB1Q9QQC9CSRB2Q9QRC9CQRB6Q9QTIPKHIYRB8Q9QVC9CIRCKA9A9A9"
+IM$(46) = "A9APRCLE9E9E9E9EPRCQA9A9A9A9APRCRE9E9E9E9EPRCZA9A9A9A9APRC1E9E9"
+IM$(47) = "E9E9EPRDCA9A9A9A9APRDFE9E9E9E9EP"
+IM$(48) = "RBOQ9QNI9IYRBTQ9QOKEQHKPQHKVRBUQ9QTI9IRRBZQ9QTKHQHKPQHKHRB0Q9QQ"
+IM$(49) = "C9CSRB5Q9QTIHKHI5KARB7Q9QUC9CKRCBQ9QYI9ICRCHA9A9A9A9APRCIE9E9E9"
+IM$(50) = "E9EPRCLA9A9A9A9APRCME9E9E9E9EPRCRA9A9A9A9APRCTE9E9E9E9EPRC1A9A9"
+IM$(51) = "A9A9APRC3E9E9E9E9EPRDFA9A9A9A9APRDIE9E9E9E9EP"
+IM$(52) = "RBSQ9QTKPQHK3RBTQ9QOI9IWRBYQ9QPKDQHKPQHKHRBZQ9QTI9ILRB4Q9QSIAKH"
+IM$(53) = "I5KHIBRB6Q9QTC9CMRCAQ9QXI9IERCEE9E9E9E9EPRCFA9A9A9A9APRCGE9E9E9"
+IM$(54) = "E9EPRCMA9A9A9A9APRCNE9E9E9E9EPRCTA9A9A9A9APRCUE9E9E9E9EPRC3A9A9"
+IM$(55) = "A9A9APRC5E9E9E9E9EPRDIA9A9A9A9AP"
 REM  ---- PICTURE-END
 SS# = 0
 SE# = NS# - 1
@@ -1317,13 +1357,25 @@ TB# = TB# + 1
 IF TB# > 2 THEN TB# = 0
 RETURN
 
+REM  A batch is four PLAY statements, one bar each: the parser's V, T,
+REM  U and duration state persists across statements and every PLAY
+REM  appends to the same queue, so four bars queue exactly as one long
+REM  string would -- which the 80-column line limit no longer allows.
+REM  Each bar restates the prefix anyway, so a bar dropped by QFULL
+REM  never leaves the next one playing with drum-kit state.
 LABEL TUNEA
-PLAY "V1T3U9S O1AO2AO3AO2AO3AO4CEAO1AO2AO4CEAO5CO4AE O1FO2FO3FO2FO3FAO4CFO1FO2FO3AO4CFAO5CO4A O1CO2CO3CO2CO3CEGO4CO1CO2CO3EGO4CEGO5C O1GO2GO3GO2GO3GBO4DGO1GO2GO3BO4DGBO5DO4B"
+PLAY "V1T3U9S O1AO2AO3AO2AO3AO4CEAO1AO2AO4CEAO5CO4AE"
+PLAY "V1T3U9S O1FO2FO3FO2FO3FAO4CFO1FO2FO3AO4CFAO5CO4A"
+PLAY "V1T3U9S O1CO2CO3CO2CO3CEGO4CO1CO2CO3EGO4CEGO5C"
+PLAY "V1T3U9S O1GO2GO3GO2GO3GBO4DGO1GO2GO3BO4DGBO5DO4B"
 MT# = TI# + 270
 RETURN
 
 LABEL TUNEB
-PLAY "V1T3U9S O1AO2AO3AO2AO3AO4CEAO1AO2AO4CEAO5CEO4A O1FO2FO3FO2FO3FAO4CFO1FO2FO3AO4CFAO5CO4A O1DO2DO3DO2DO3DFAO4DO1DO2DO3FAO4DFAO5D O1EO2EO3EO2EO3E#GBO4EO1EO2EO3#GBO4E#GBO5E"
+PLAY "V1T3U9S O1AO2AO3AO2AO3AO4CEAO1AO2AO4CEAO5CEO4A"
+PLAY "V1T3U9S O1FO2FO3FO2FO3FAO4CFO1FO2FO3AO4CFAO5CO4A"
+PLAY "V1T3U9S O1DO2DO3DO2DO3DFAO4DO1DO2DO3FAO4DFAO5D"
+PLAY "V1T3U9S O1EO2EO3EO2EO3E#GBO4EO1EO2EO3#GBO4E#GBO5E"
 MT# = TI# + 270
 RETURN
 

examples/megademo/vaporwave.py

@@ -58,7 +58,14 @@ SKIP = "Q"
 ROWREC = "R"
 LENCH = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
 MAXRUN = len(LENCH)
-PAYLOAD = 240
+
+# The interpreter reads source through an 80-byte line buffer and refuses
+# any line that fills it (AKBASIC_MAX_LINE_LENGTH, sink_stdio.c), so a
+# stored line is at most 78 characters plus its newline. 'IM$(NN) = "' and
+# the closing quote spend 12 of those; 64 keeps the emitted lines under
+# the ceiling with margin to spare while the index stays two digits.
+PAYLOAD = 64
+MAXLINE = 78
 
 SUN_CX, SUN_CY, SUN_R = 80, 50, 30
 HORIZON = 74
@@ -206,13 +213,32 @@ def encode_delta(prev, cur):
 
 
 def chop(blob):
-    return [blob[i:i + PAYLOAD] for i in range(0, len(blob), PAYLOAD)]
+    """Split a stream into strings of at most PAYLOAD characters, cutting
+    only between records. The decoder reads a record's tail characters
+    with MID on the string it is walking, so a run (two characters) or a
+    row record (three) that straddled two IM$ entries would decode as
+    garbage; DRAWSTREAM only carries the cursor, never a partial record."""
+    out, cur = [], ""
+    p = 0
+    while p < len(blob):
+        n = 3 if blob[p] == ROWREC else 2
+        if len(cur) + n > PAYLOAD:
+            out.append(cur)
+            cur = ""
+        cur += blob[p:p + n]
+        p += n
+    if cur:
+        out.append(cur)
+    return out
 
 
-def simulate(raster, blob):
+def simulate(raster, blob, x=0, y=0):
     """Apply one encoded stream to a raster exactly the way the BASIC
-    decoder does, skips-draw-nothing and all."""
-    x = y = p = 0
+    decoder does, skips-draw-nothing and all. The cursor comes in and
+    goes back out because DRAWSTREAM carries it from one IM$ entry to
+    the next -- decoding the chopped strings one at a time with the
+    cursor threaded through is exactly what the demo will execute."""
+    p = 0
     while p < len(blob):
         c = blob[p]
         if c == ROWREC:
@@ -230,20 +256,31 @@ def simulate(raster, blob):
             x = 0
             y += 1
         p += 2
+    return raster, x, y
+
+
+def simulate_lines(raster, lines):
+    """One stream as its chopped strings, cursor carried across the
+    boundaries the way DRAWSTREAM carries X# and Y#."""
+    x = y = 0
+    for line in lines:
+        raster, x, y = simulate(raster, line, x, y)
     return raster
 
 
-def verify(frames, base_blob, delta_blobs):
+def verify(frames, base_lines, delta_line_groups):
     """The base must reproduce frame 0 exactly, and each delta must
     carry the raster exactly to the next frame. A skip leaves the cell
     the encoder promised was already right, so equality is total and
-    any difference at all is an encoder bug."""
+    any difference at all is an encoder bug. This decodes the CHOPPED
+    strings, not the blobs, so a chop that split a record would fail
+    here instead of corrupting the screen."""
     raster = [[1] * W for _ in range(H)]
-    raster = simulate(raster, base_blob)
+    raster = simulate_lines(raster, base_lines)
     assert raster == frames[0], "base stream does not reproduce frame 0"
-    for i, blob in enumerate(delta_blobs):
+    for i, lines in enumerate(delta_line_groups):
         want = frames[(i + 1) % PHASES]
-        raster = simulate(raster, blob)
+        raster = simulate_lines(raster, lines)
         assert raster == want, "delta %d does not reproduce its frame" % i
 
 
@@ -261,6 +298,9 @@ def emit_block(base_lines, delta_ranges, all_lines):
     for i, s in enumerate(all_lines):
         out.append('IM$(%d) = "%s"' % (i, s))
     out.append("REM  ---- PICTURE-END")
+    for line in out:
+        assert len(line) <= MAXLINE, "emitted line over %d chars: %r" % (
+            MAXLINE, line)
     return out
 
 
@@ -303,15 +343,15 @@ def main():
     base_lines = chop(base_blob)
     all_lines = list(base_lines)
     delta_ranges = []
-    delta_blobs = []
+    delta_line_groups = []
     for i in range(PHASES):
         blob = encode_delta(frames[i], frames[(i + 1) % PHASES])
-        delta_blobs.append(blob)
         lines = chop(blob)
+        delta_line_groups.append(lines)
         delta_ranges.append((len(all_lines), len(all_lines) + len(lines) - 1))
         all_lines.extend(lines)
-    verify(frames, base_blob, delta_blobs)
-    dbytes = sum(len(b) for b in delta_blobs)
+    verify(frames, base_lines, delta_line_groups)
+    dbytes = sum(len(l) for g in delta_line_groups for l in g)
     print("base %d bytes in %d strings; video %d bytes in %d strings; "
           "%d strings total" %
           (sum(len(s) for s in base_lines), len(base_lines), dbytes,

tests/language/arrays_in_parameter_lists.bas

@@ -1,6 +1,6 @@
 10 REM An array reference used as a function argument, and as one of several.
 20 REM An identifier's subscript list used to hang off .right, which is also
-30 REM where an argument list chains its arguments -- so the arity counter walked
+30 REM where an argument list chains its arguments; the arity counter walked
 40 REM straight into the subscripts and refused the call. TODO.md section 4.
 50 DIM C#(4)
 60 C#(1) = -9

tests/language/audio/filter_refused.bas

@@ -1,6 +1,6 @@
-10 REM FILTER has no device capability behind it -- akgl_audio_* synthesises and
-20 REM mixes but has no filter stage, and SDL3 supplies no primitive to build one
-30 REM from. It is refused rather than silently ignored, so a program that asked
+10 REM FILTER has no device capability; akgl_audio_* synthesises and mixes but
+20 REM has no filter stage, and SDL3 supplies no primitive to build one from.
+30 REM It is refused rather than silently ignored, so a program that asked
 40 REM for a low-pass finds out it did not get one.
 50 PRINT "BEFORE"
 60 FILTER 1000, 1, 0, 0, 5

tests/language/audio/no_device.bas

@@ -1,4 +1,4 @@
-10 REM The standalone driver lends the script no audio device. ENVELOPE, VOL and
+10 REM The standalone driver lends the script no audio device. ENVELOPE, VOL,
 20 REM TEMPO only change interpreter state, so they work regardless; SOUND and
 30 REM PLAY need the device and must name themselves when there is none.
 40 ENVELOPE 1, 5, 9, 12, 2

tests/language/functions/recursion.bas

@@ -1,6 +1,6 @@
-10 REM A DEF call takes its environment from the pool, one per call, exactly as
+10 REM A DEF call takes one environment from the pool, exactly as
 20 REM GOSUB does. It used to be owned by the funcdef and reset on every call,
-30 REM which cost two silent defects: two calls in one expression shared a slot,
+30 REM which cost two silent defects: calls in one expression shared a slot,
 40 REM and recursion never came back at all.
 50 DEF FACT(N#)
 60 IF N# <= 1 THEN RETURN 1
@@ -15,9 +15,9 @@
 150 DEF DBL(N#) = N# * 2
 160 PRINT DBL(10) + DBL(1)
 170 PRINT DBL(1) + DBL(10) + DBL(100)
-180 REM Depth answers to the environment pool now, so runaway recursion reports
-190 REM "Environment pool exhausted" rather than hanging. It is not exercised here
-200 REM because the statement containing a failed call still prints a junk value
-210 REM afterwards -- a separate, pre-existing defect recorded in TODO.md, and one
-220 REM this golden file would pin if it went in. tests/user_functions.c asserts
+180 REM Depth answers to the environment pool, so runaway recursion reports
+190 REM "Environment pool exhausted" rather than hanging. It is not exercised
+200 REM here because the failed statement still prints junk afterwards;
+210 REM this is a separate defect in TODO.md, and one this golden file
+220 REM would pin if it went in. tests/user_functions.c asserts
 230 REM the message instead.

tests/language/graphics/argument_errors.bas

@@ -1,4 +1,4 @@
-10 REM A range check reported through the driver, end to end. The program stops
+10 REM A range check reported through the driver, end to end. The program
 20 REM at the first error, so this file covers one; the rest of the checks are
 30 REM asserted in tests/graphics_verbs.c against the recording backend.
 40 PRINT "BEFORE"

tests/language/graphics/no_device.bas

@@ -1,5 +1,5 @@
 10 REM The standalone driver lends the script no graphics device.
-20 REM COLOR, LOCATE and SCALE only touch interpreter state and must still work.
+20 REM COLOR, LOCATE and SCALE touch interpreter state and must still work.
 30 COLOR 1, 3
 40 LOCATE 40, 50
 50 SCALE 1, 640, 400

tests/language/housekeeping/verbs.bas

@@ -1,5 +1,5 @@
-10 REM Group B: the housekeeping verbs. None of these is in the Go reference --
-20 REM they are on its own unimplemented list -- so what each one means here is
+10 REM Group B: housekeeping verbs. None is in the Go reference --
+20 REM they are on its unimplemented list -- so each meaning here is
 30 REM a decision, recorded in src/runtime_housekeeping.c beside the verb.
 40 A# = 1 : B# = 2
 50 PRINT A# : PRINT B#
@@ -11,7 +11,7 @@
 110 P#(2) = 7 : Q#(2) = 9
 120 SWAP P#, Q#
 130 PRINT P#(2) : PRINT Q#(2)
-140 REM TRON prints each line number inline before the line runs, as a C128 does.
+140 REM TRON prints each line number inline, as a C128 does.
 150 TRON
 160 PRINT "TRACED"
 170 TROFF

tests/language/numeric/octal_literal.bas

@@ -1,7 +1,7 @@
-10 REM A leading zero is padding, not a radix. The reference selects base 8 for
-20 REM any lexeme starting with 0, so 010 printed 8 and 08 was a parse error --
-30 REM TODO.md section 6 item 10, fixed. Commodore BASIC has no octal literals.
-40 REM 0x is the one prefix that changes the base, and it now reaches the scanner
+10 REM A leading zero is padding, not a radix. The reference selected base 8
+20 REM for lexemes starting with 0; 010 printed 8 and 08 was a parse error --
+30 REM TODO.md section 6 item 10 is fixed; Commodore BASIC has no octal.
+40 REM 0x is the one prefix that changes the base, and now reaches the scanner
 50 REM whole: that was section 6 item 15.
 60 PRINT 010
 70 PRINT 08

tests/language/numeric/truth_value_arithmetic.bas

@@ -1,12 +1,12 @@
 10 REM A truth value carries its payload in boolvalue, not floatval. The three
 20 REM numeric operators were `if ( INTEGER ) ... else <treat as float>`, and
-30 REM that else was a catch-all rather than a float branch -- so a truth value
+30 REM that else was a catch-all, not a float branch -- so a truth value
 40 REM on the LEFT computed 0 - 1 into a field nothing reads, kept its BOOLEAN
 50 REM type, and printed `true` instead of -2. Silent, and wrong twice over.
 60 A# = 1
 70 PRINT (A# == 1)
-80 REM On the RIGHT it stays legal and stays -1, which is the same property that
-90 REM lets AND and OR double as logical operators. Refusing it here would have
+80 REM On the RIGHT it stays legal and stays -1, the same property that
+90 REM lets AND and OR act as logical operators. Refusing it would have
 100 REM broken every condition in the language.
 110 PRINT 5 - (A# == 1)
 120 PRINT 5 * (A# == 1)

tests/language/statements/multiple_per_line.bas

@@ -1,11 +1,11 @@
-10 REM Statements separated by colons. The COLON token existed from the start of
-20 REM the port and nothing consumed it, so a line could hold only one statement.
+10 REM Statements separated by colons. The COLON token existed from the start;
+20 REM nothing consumed it, so a line could hold only one statement.
 30 PRINT "A" : PRINT "B"
 40 A# = 1 : B# = 2 : PRINT A# + B#
-50 REM An empty statement is not an error: a trailing separator, or a run of them.
+50 REM Empty statements are valid: a trailing separator or runs of them.
 60 PRINT "C" :
 70 PRINT "D" :: PRINT "E"
-80 REM Everything after THEN belongs to the condition, which is BASIC 7.0 and is
+80 REM Everything after THEN belongs to the condition, as in BASIC 7.0, and is
 90 REM not something the reference had an opinion about -- it never got here.
 100 IF 1 == 1 THEN PRINT "TRUE-1" : PRINT "TRUE-2"
 110 IF 1 == 0 THEN PRINT "NEVER-1" : PRINT "NEVER-2"

tests/language/structures/missing_field.bas

@@ -1,5 +1,5 @@
-10 REM A field name is checked against a closed set the program declared, which
-20 REM is the one thing in this language whose valid spellings are written down.
+10 REM A field name is checked against the closed set the program declared;
+20 REM this is the one thing whose valid spellings are written down.
 30 REM A misspelled *variable* is still silent -- see the last two lines.
 40 TYPE RECT
 50   W#

tests/language/structures/parameters.bas

@@ -17,7 +17,7 @@
 170 RETURN B@.W#
 180 PRINT WIDEN(A@)
 190 PRINT A@.W#
-200 REM To change one on purpose, pass a pointer. Assignment copies a pointer's
+200 REM To change one on purpose, pass a pointer. Assignment copies its
 210 REM reference, so the callee is looking at the caller's own record.
 220 DIM Q@ AS PTR TO CRATE
 230 POINT Q@ AT A@
@@ -37,7 +37,7 @@
 370 N2@.COUNT# = 20
 380 POINT N1@.TAIL@ AT N2@
 390 DEF TOTAL(P@ AS PTR TO NODE)
-395 REM A pointer is true when it points at something, which is how a walk knows
+395 REM A pointer is true when it points at something, so a walk knows
 396 REM where the list ends. NOT is the bitwise operator here, so the test is
 397 REM written the positive way round.
 400 IF P@->TAIL@ THEN RETURN P@->COUNT# + TOTAL(P@->TAIL@)

tests/language/structures/records.bas

@@ -1,4 +1,4 @@
-10 REM A TYPE declares its fields; each takes its own type from its own suffix,
+10 REM A TYPE declares its fields; each takes its type from its own suffix,
 20 REM which is the same rule every other name in this language follows.
 30 TYPE COORD
 40   X#

tests/language/structures/reserved_names.bas

@@ -1,6 +1,6 @@
 10 REM A type name and a field name are bare words, and so is every verb, so
 20 REM they share a namespace whether we like it or not. Both are refused with
-30 REM the same rule the scanner already applies to variable names -- and a type
+30 REM the scanner applies the same rule to variable names -- and a type
 40 REM name is refused by the prescan, which can say so plainly rather than
 50 REM leaving the parser to report "Expected expression or literal".
 60 TYPE POINT

tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.bas

@@ -1,6 +1,6 @@
 10 REM This shows the waitingForCommand utility in the BasicEnvironment
 11 REM when we have a nested for loop. The inner loop SHOULD execute, but
-12 REM the outer loop should NOT execute. Therefore, neither loop should execute.
+12 REM the outer loop should NOT execute; neither loop should execute.
 20 FOR I# = 1 TO 0
 25 FOR J# = 2 TO 4
 30 PRINT "waitingForCommand FAILS if this is seen"
@@ -8,4 +8,4 @@
 35 NEXT J#
 40 NEXT I#
 50 PRINT "SUCCESS"
-80 QUIT
+80 QUIT

tests/reference/language/functions/mod.bas

@@ -1,6 +1,6 @@
 10 PRINT MOD(10, 3)
 20 PRINT MOD(12, 5)
 30 PRINT MOD(4, 2)
-40 REM MOD() ONLY WORKS WITH INTEGERS - RESULTS WITH FLOATING POINT ARE UNRELIABLE
+40 REM MOD() ONLY WORKS WITH INTEGERS; FLOATING POINT RESULTS ARE UNRELIABLE
 50 REM PRINT MOD(1.2, 0.4)
 60 REM THERE IS NO ERROR THROWN HERE. JUST DONT DO IT.