# COMMAND_SPEC.md

System Commands

ABOUT
BOOK
CATALOG
CLEAR
CLS
CLOSE #1
COLOR foreground
COLOR foreground,background
HELP
INPUT #1, A$
LINE INPUT #1, A$
LIST
LOAD
LOAD "FIL.BAS"
LOCATE row,column
MODE AMBER
MODE DOS
MODE GREEN
NEW
NEWS
OPEN "IN.TXT" FOR INPUT AS #1
OPEN "OUT.TXT" FOR OUTPUT AS #1
PRINT #1, "TEXT"
RUN
RUN "PROGRAM.BAS"
SAVE
SAVE "FIL.BAS"
SOUND frequency,duration

Keyboard Commands

CTRL+C - BREAK AT LINE
ESC - BREAK AT LINE

Commands are case-insensitive.
Program source casing and spacing are preserved for LIST, SAVE, and LOAD.

`LOAD` opens a local `.BAS` text-file picker.
`LOAD "FIL.BAS"` loads a bundled sample from `examples/` when it is listed in the catalog.
`SAVE` downloads `CLASSIC.BAS`.
`SAVE "FIL.BAS"` downloads the current program using the quoted filename.
`RUN "PROGRAM.BAS"` loads a bundled sample and runs it immediately.
`NEWS` prints the latest Classic BASIC new release notes.
`CATALOG` lists bundled samples.
`CLEAR` clears variables and arrays without deleting the stored program.
`BOOK` opens the Classic BASIC guide book link.
Display mode commands update terminal colors for the current session. Fresh loads and restarts begin in Green mode.
`COLOR foreground` changes the current DOS text color only.
`COLOR foreground,background` changes the current DOS text and background color.
Printed lines keep the colors that were active when they were printed.
In Green or Amber mode, `COLOR` is visually ignored for text and graphics. Nonzero graphics colors render in the active monochrome theme color; color 0 remains black so programs can clear graphics areas. DOS mode is the only true multi-color display mode.

Core BASIC statements include PRINT, INPUT, LET, assignment, IF/THEN/ELSE, GOTO, GOSUB/RETURN, FOR/NEXT, WHILE/WEND, DIM, DATA, READ, RESTORE, REM, END, STOP, CLS, and graphics statements.
`PRINT "TEXT";` keeps the next PRINT on the same output line.
`LOCATE row,column` moves the text cursor to a 1-based screen position before the next PRINT.
Press Escape or Ctrl+C while a program is running to stop it and return to the prompt. Ctrl+Break/Pause is supported when the browser exposes it. Touch/mobile devices without recent keyboard use show a small theme-aware BREAK button while a program is running.
`SOUND frequency,duration` plays a browser-safe tone. Duration uses GW-BASIC-style clock ticks, about 18.2 ticks per second.
`SLEEP seconds` pauses program execution for a browser-safe duration, capped at 5 seconds.
Sequential file output downloads to the user's computer on CLOSE. Sequential file input uses the browser file picker. No BASIC file I/O touches the server.
`CHR$(N)` returns the ASCII character for code N.
`ASC(S$)` returns the ASCII code of the first character in S$.
`DIM A(N)` creates a numeric array with indexes 0 through N.
`DIM A$(N)` creates a string array with indexes 0 through N.
`DIM A(N,N)` and larger multi-dimensional arrays are supported.

Current game catalog:

LOAD "BLACKJACK.BAS"
LOAD "BLOCK.BAS"
LOAD "FOOTBALL.BAS"
LOAD "HANGMAN.BAS"
LOAD "HIGHLOW.BAS"
LOAD "RHOP.BAS"

BLOCK DROP controls:

LEFT ARROW or A = move left
RIGHT ARROW or D = move right
DOWN ARROW or S = soft drop
UP ARROW, W, or SPACE = rotate
P = pause/resume
Q or ESC = quit

ROAD HOPPER controls:

LEFT ARROW or A = move left
RIGHT ARROW or D = move right
UP ARROW or W = move up
DOWN ARROW or S = move down
P = pause/resume
Q or ESC = quit

Graphics Commands

SCREEN 1
PSET (10,10),15
PRESET (10,10)
LINE (0,0)-(100,50),10
LINE (10,10)-(80,80),14,B
CIRCLE (160,100),40,11
PAINT (160,100),12
POINT(100,50)
DRAW "R40D20L40U20"
GET (0,0)-(20,20),A
PUT (40,40),A
VIEW (0,0)-(319,199)
WINDOW (0,0)-(100,100)