akbasic/examples/breakout/characters/breakout.bas

REM ####################################################################
REM BREAKOUT
REM
REM One hundred percent BASIC, for the AKGL BASIC interpreter.
REM   ../akbasic/build-akgl/basic breakout.bas
REM
REM The ball and the paddle are sprites, defined from DATA in this listing.
REM The bricks, the HUD and the messages are characters in the text grid.
REM Nothing here loads an asset and nothing here uses DRAW, BOX or CIRCLE:
REM the drawing verbs do not survive a frame in this interpreter, while the
REM text grid and the sprites are both redrawn from persistent state every
REM frame. See README.md for the whole list of things that shaped this.
REM
REM Three rules this listing never breaks, each one earned the hard way:
REM   * A row of text is written whole, from column 0. CHAR terminates the
REM     row where it stops, so writing at column N erases N+1 onwards.
REM   * Mixed + and - are parenthesised. This parser reads a - b + c as
REM     a - (b + c), and matches only ONE unparenthesised AND or OR.
REM   * The main loop is a GOTO loop. Every loop and every GOSUB takes one
REM     of 32 scopes, and a state change jumping out of a DO would leak one
REM     every time; thirty-two lives later the program stops.
REM
REM Two more rules were true when this was written and are not any more.
REM They are recorded because the shape of the listing is still theirs:
REM   * Every name is created once, in the pool block below. A name first
REM     created inside a GOSUB or a FOR used to cost a value slot that was
REM     never handed back, out of 4096 for the whole run, and this game died
REM     after twenty-five seconds because of it. A scalar is free now; only
REM     the DIMs below still have to be up here. TODO.md section 6 item 30.
REM   * Writing PAST the terminator of a short row used to draw nothing at
REM     all. The gap is padded with spaces now. TODO.md section 6 item 32.
REM
REM Written by Claude Opus (1M)
REM ####################################################################

LABEL SETUP
SCNCLR

REM --- geometry -------------------------------------------------------
REM Nothing here is assumed. RGR(1) and RGR(2) are the window in pixels,
REM RGR(3) and RGR(4) are one character cell, and RWINDOW gives the text
REM grid in columns and rows -- so the game fits whatever window the host
REM opened and whatever font it loaded. Everything below is derived from
REM these six, including the ball's speed relative to the wall.
REM
REM The first version of this file had CW# = 16 and CH# = 16 written out,
REM measured by hand against the bundled C64_Pro_Mono at 16 points, because
REM there was no way to ask -- and that was the one thing in the listing
REM that would break on a different font. RGR(3) and RWINDOW were added to
REM the interpreter because of it.
SCW# = RGR(1)
SCH# = RGR(2)
CW# = RGR(3)
CH# = RGR(4)
COLS# = RWINDOW(1)
ROWS# = RWINDOW(0)

REM --- the brick wall, in cells ---------------------------------------
BRW# = 4
BCOLS# = 10
BROWS# = 6
BTOP# = 4
BLEFT# = (COLS# - (BRW# * BCOLS#)) / 2

REM --- the play area, in pixels ---------------------------------------
TOPY# = 2 * CH#
MAXX# = SCW# - 8
PW# = 144
PY# = 528
LOSEY# = PY# + 32
MSGROW# = 35
TITROW# = 20
PSPD# = 10

REM --- pools ----------------------------------------------------------
REM Every name in the program is created HERE.
REM
REM One reason still stands. A GOSUB gets its own scope: assignment walks up
REM the chain and finds an outer variable, but a name first seen inside a
REM subroutine is created in the subroutine and dies at RETURN -- so HIT#
REM and BI# would mean nothing to the caller if they were not already out
REM here, and HITTEST would answer into two variables nobody can read.
REM
REM The other has been fixed. A scalar used to cost a value slot for good --
REM the pool is a bump allocator with no free, and recycling a variable took
REM fresh slots, so 4096 creations ended the run whenever they happened. A
REM scalar now lives in the variable itself and costs the pool nothing; only
REM the DIMs still spend, which is why they are the part that has to be up
REM here. The rest of this block is habit, and harmless.
DIM BR#(60)
DIM SB#(63)
DIM SP#(63)
DIM LAY$(6)
DIM BSG$(6)

SCORE# = 0
HIGH# = 0
LIVES# = 3
LEVEL# = 1
LEFTN# = 0
BSPD# = 4
STATE# = 0
DEMO# = 0
PAUSED# = 0
HELD# = 0
PDIR# = 0
PDEC# = 0
PX# = 0
BX# = 0
BY# = 0
BVX# = 0
BVY# = 0
OX# = 0
OY# = 0
K# = 0
HIT# = 0
SX# = 0
SY# = 0
A# = 0
D% = 0.0
M# = 0
PVX# = 0
DOFF# = 0
STALL# = 0
NUDGE# = 0
BI# = 0
BR2# = 0
RB# = 0
CB# = 0
RC# = 0
CC2# = 0
TX# = 0
TY# = 0
PTS# = 0
V# = 0
L# = 0
C2# = 0
D# = 0
M# = 0
X2# = 0
X3# = 0
Z# = 0
BB# = 0
RX# = 0
N# = 0
MROW# = 0
RMAX# = 2
RND# = 0
SND# = 0
P$ = ""
H$ = ""
S$ = ""
T$ = ""
MSG$ = ""
BSEG$ = ""
FRAME$ = ""
I# = 0
R# = 0
R2# = 0
C# = 0
CC# = 0
KI# = 0
T# = 0

REM Brick faces, one per wall row. CHAR ignores its colour argument --
REM the sink draws in one colour -- so the rows are told apart by shape.
BSG$(0) = "[##]"
BSG$(1) = "[##]"
BSG$(2) = "[==]"
BSG$(3) = "[==]"
BSG$(4) = "[--]"
BSG$(5) = "[--]"

REM --- the seed -------------------------------------------------------
REM There is no RND in this dialect. TI# is jiffies off the host's clock
REM and is host uptime rather than zero-based, which makes it a fine seed.
SEED# = TI#

REM The ceiling, drawn once. TOPY# is the bottom edge of this row, so the
REM ball turns against something the player can see rather than against an
REM invisible line two rows down from the top of the window.
FRAME$ = "=" * COLS#
CHAR 1, 0, 1, FRAME$

GOSUB MKSPR
GOSUB SNDPROBE
COLLISION 2, BRICKHIT
GOTO TITLE

REM ####################################################################
REM  SPRITES
REM ####################################################################

LABEL MKSPR
FOR I# = 0 TO 62
  READ SB#(I#)
NEXT I#
FOR I# = 0 TO 62
  READ SP#(I#)
NEXT I#
SPRSAV SB#, 1
SPRITE 1, 1, 2
SPRSAV SP#, 2
SPRSAV SP#, 3
SPRSAV SP#, 4
SPRITE 2, 1, 15, 0, 1, 0
SPRITE 3, 1, 15, 0, 1, 0
SPRITE 4, 1, 15, 0, 1, 0
RETURN

REM ####################################################################
REM  SOUND
REM
REM SOUND refuses on a machine with no audio device, and an untrapped
REM refusal would end the game. Ask once, remember the answer, and never
REM ask again -- the game is silent where there is nothing to play on.
REM ####################################################################

LABEL SNDPROBE
SND# = 1
TRAP NOAUDIO
SOUND 1, 2000, 1
TRAP
RETURN

LABEL NOAUDIO
SND# = 0
RESUME NEXT

LABEL BEEPB
IF SND# = 1 THEN SOUND 1, 12000, 2
RETURN

LABEL BEEPP
IF SND# = 1 THEN SOUND 2, 6000, 3
RETURN

LABEL BEEPW
IF SND# = 1 THEN SOUND 3, 9000, 1
RETURN

LABEL BEEPL
IF SND# = 1 THEN SOUND 1, 1500, 20
RETURN

REM ####################################################################
REM  TITLE AND ATTRACT MODE
REM
REM The title screen plays itself. It is also how this game gets tested
REM without a human at the keyboard.
REM ####################################################################

LABEL TITLE
DEMO# = 1
SCORE# = 0
LIVES# = 3
LEVEL# = 1
BSPD# = 4
PAUSED# = 0
GOSUB LOADLAY
GOSUB BUILDW
GOSUB DRAWW
GOSUB DRAWHUD
GOSUB TITTEXT
GOSUB SERVE
STATE# = 0
GOTO TICK

LABEL TITTEXT
MROW# = TITROW#
MSG$ = "B R E A K O U T"
GOSUB SHOWAT
MROW# = TITROW# + 2
MSG$ = "PRESS SPACE TO PLAY"
GOSUB SHOWAT
MROW# = TITROW# + 4
MSG$ = "LEFT AND RIGHT MOVE   P PAUSES   Q QUITS"
GOSUB SHOWAT
MROW# = TITROW# + 6
MSG$ = "ATTRACT MODE"
GOSUB SHOWAT
RETURN

LABEL CLRTIT
MROW# = TITROW#
GOSUB CLRAT
MROW# = TITROW# + 2
GOSUB CLRAT
MROW# = TITROW# + 4
GOSUB CLRAT
MROW# = TITROW# + 6
GOSUB CLRAT
RETURN

REM ####################################################################
REM  GAME AND LEVEL SETUP
REM ####################################################################

LABEL NEWGAME
DEMO# = 0
SCORE# = 0
LIVES# = 3
LEVEL# = 1
BSPD# = 4
PAUSED# = 0
GOSUB CLRTIT
GOSUB NEWLEV
STATE# = 0
GOTO TICK

LABEL NEWLEV
GOSUB LOADLAY
GOSUB BUILDW
GOSUB DRAWW
GOSUB DRAWHUD
GOSUB SERVE
MSG$ = "PRESS SPACE TO LAUNCH"
GOSUB SHOWMSG
RETURN

REM Three layouts, then round again with a faster ball. RESTORE takes a
REM label -- it wants a line and a label evaluates to one -- so a layout is
REM simply a named place in the DATA stream.
LABEL LOADLAY
N# = MOD((LEVEL# - 1), 3)
IF N# = 0 THEN RESTORE LAY1
IF N# = 1 THEN RESTORE LAY2
IF N# = 2 THEN RESTORE LAY3
FOR R# = 0 TO 5
  READ LAY$(R#)
NEXT R#
RETURN

LABEL BUILDW
LEFTN# = 0
FOR R# = 0 TO 5
  S$ = LAY$(R#)
  GOSUB BUILDR
NEXT R#
RETURN

REM One wall row. Each brick is registered with SOLID as well as recorded in
REM BR#(), so the interpreter can answer "did the ball hit a brick" and, more
REM usefully, "which one and which way is out". The id is the array index plus
REM one, so nothing has to be looked up on the way back.
LABEL BUILDR
FOR C# = 0 TO 9
  T$ = MID(S$, C#, 1)
  I# = (R# * BCOLS#) + C#
  BR#(I#) = 0
  IF T$ = "1" THEN BR#(I#) = 1
  IF T$ = "1" THEN LEFTN# = LEFTN# + 1
  SX# = (BLEFT# + (C# * BRW#)) * CW#
  SY# = (BTOP# + R#) * CH#
  IF T$ = "1" THEN SOLID I# + 1, SX#, SY#, SX# + (BRW# * CW#), SY# + CH#
  IF T$ = "0" THEN SOLID I# + 1
NEXT C#
RETURN

LABEL DRAWW
FOR R# = 0 TO 5
  BR2# = R#
  GOSUB DRAWBR
NEXT R#
RETURN

REM One brick row, rebuilt whole and written in a single CHAR. Anything
REM else would truncate the row at the first character it wrote.
LABEL DRAWBR
S$ = ""
IF BLEFT# > 0 THEN S$ = " " * BLEFT#
BSEG$ = BSG$(BR2#)
FOR CC# = 0 TO 9
  I# = (BR2# * BCOLS#) + CC#
  IF BR#(I#) = 1 THEN S$ = S$ + BSEG$
  IF BR#(I#) = 0 THEN S$ = S$ + "    "
NEXT CC#
R2# = BTOP# + BR2#
CHAR 1, 0, R2#, S$
RETURN

REM Put the ball back on the paddle, pointing up, left or right at random.
LABEL SERVE
PX# = (SCW# - PW#) / 2
HELD# = 1
IF DEMO# = 1 THEN HELD# = 0
BX# = PX# + ((PW# / 2) - 4)
BY# = PY# - 10
RMAX# = 2