Upload BazzBasic-AI-guide-01-05-2026.txt

Updated to BazzBasic version 1.4 released 01.05.2026

BazzBasic-AI-guide-01-05-2026.txt

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+---
+name: bazzbasic
+description: "BazzBasic BASIC interpreter language reference. Use when writing, debugging, or explaining BazzBasic code (.bas files). Triggers on: BazzBasic syntax, $ and # variable suffixes, SDL2 graphics in BASIC, SCREEN/DRAWSHAPE/LOADIMAGE commands, DEF FN functions, BazzBasic file I/O, sound commands, or any question about BazzBasic features. Always use this skill before writing any BazzBasic code."
+
+doc. date: 30.04.2026 (dd.mm.yyyy)
+
+filename: BazzBasic-AI-guide-ddmmyyyyX.txt (ddmmyyyy = date of last update) (X is small alphabet "abcd..." presenting daily version incase two versions are released in same day)
+
+IE:
+BazzBasic-AI-Guide30042026.txt ' version released 30th April 2026
+BazzBasic-AI-Guide30042026b.txt ' version released 30th April 2026, second in same date
+
+---
+
+# BazzBasic Language Reference
+**Version:** 1.3b | **Author:** Kristian Virtanen (EkBass) | **Platform:** Windows x64  
+**Homepage:** https://ekbass.github.io/BazzBasic/  
+**GitHub:** https://github.com/EkBass/BazzBasic  
+**Manual:** https://ekbass.github.io/BazzBasic/manual/#/  
+**Examples:** https://github.com/EkBass/BazzBasic/tree/main/Examples  
+**Rosetta Code:** https://rosettacode.org/wiki/Category:BazzBasic  
+**Rosetta Code solutions:** https://github.com/EkBass/BazzBasic/tree/main/Examples/rosetta-code  
+**BazzBasic-AI-Guide:** https://huggingface.co/datasets/EkBass/BazzBasic_AI_Guide  
+**BazzBasic Beginner's Guide:** https://github.com/EkBass/BazzBasic-Beginners-Guide/releases  
+**Communities:** https://ekbass.github.io/BazzBasic/communities.html
+
+---
+
+## Critical Rules Read First
+
+| Rule | Detail |
+|------|--------|
+| Variables end with `$` | `name$`, `score$`, `x$` |
+| Constants end with `#` | `MAX#`, `PI#`, `TITLE#` |
+| Arrays declared with `DIM`, end with `$` | `DIM items$` |
+| First use of variable requires `LET` | `LET x$ = 0`  after that `x$ = x$ + 1` |
+| FOR and INPUT auto-declare, no LET needed | `FOR i$ = 1 TO 10` |
+| Functions defined **before** they are called | Put at top or INCLUDE |
+| Function name ends with `$`, called with `FN` | `FN MyFunc$(a$, b$)` |
+| Function return value **must** be used | `PRINT FN f$()` or `LET v$ = FN f$()` |
+| Arrays **cannot** be passed to functions directly | Pass individual elements, or serialize to JSON string  see *Passing Arrays to Functions* section |
+| Case-insensitive | `PRINT`, `print`, `Print` all work |
+| `+` operator does both add and concatenate | `"Hi" + " " + name$` |
+| Division always returns float | `10 / 3` → `3.333...` |
+| Division by zero returns `0` (no error) | Guard with `IF b$ = 0 THEN ...` if needed |
+| No integer-division operator | Use `INT(a / b)`, `FLOOR(a / b)`, or `CINT(a / b)` |
+| Errors halt the program | No `TRY`/`CATCH` or `ON ERROR`  line-numbered message printed |
+
+---
+
+## Common AI Mistakes (avoid these)
+
+These are the patterns LLMs most often produce when extrapolating from QBASIC, FreeBASIC, or VB. None of them are valid BazzBasic.
+
+```basic
+' WRONG                                		' CORRECT
+LET x = 5                               	LET x$ = 5
+LET MAX = 10                            	LET MAX# = 10
+score$ = 0          ' first use           	LET score$ = 0
+DEF FN doStuff(a, b)                      	DEF FN DoStuff$(a$, b$)
+FN MyFunc$(5)       ' return ignored      	LET v$ = FN MyFunc$(5)
+LET handle$ = LOADIMAGE("x.png")          	LET HANDLE# = LOADIMAGE("x.png")
+CLS                 ' in graphics mode    	LINE (0,0)-(W,H), 0, BF
+PRINT "x:", x$      ' in graphics mode    	DRAWSTRING "x:" + STR(x$), 10, 10, RGB(255,255,255)
+FSTRING("Hi {{name$}}") ' Python-style    	FSTRING("Hi {{-name$-}}")     ' triple-char markers
+ISSET(arr$(0))   ' expecting error        	' returns 0 silently  ISSET only sees scalars
+LET x$ = a$ + _ ' VBA continuation        	LET x$ = a$ +     ' just leave the operator
+LET x$ = a$ + \ ' Python continuation     	LET x$ = a$ +     ' or open a paren  see Line Continuation
+```
+
+**Two more traps that don't fit the table:**
+
+- Inside `DEF FN` you can read `#` constants from the outer scope but **not** `$` variables. Pass them as parameters.
+- Arrays cannot be passed to a function. Serialize with `ASJSON()` and rebuild inside the function with `ASARRAY()`  see *Passing Arrays to Functions* below.
+
+---
+
+## Minimal Valid Program
+
+```basic
+[inits]
+    LET name$ = "World"
+
+[main]
+    PRINT "Hello, " + name$
+END
+```
+
+Programs flow top to bottom. `[inits]` and `[main]` are organizational labels, not required syntax  the file would also run without them. `END` halts execution; place it at the end of the main flow so control doesn't fall through into subroutines or function definitions.
+
+---
+
+## When Generating BazzBasic Code
+
+- Always declare variables with `LET` on first use; subsequent uses don't need it
+- Always include the `$` (variable) or `#` (constant) suffix
+- Place `DEF FN` definitions at the top of the file or via `INCLUDE`
+- Store every `LOADIMAGE` / `LOADSOUND` / `LOADSHAPE` handle as a `#` constant
+- In graphics mode, prefer `LINE (0,0)-(W,H), 0, BF` over `CLS`, and `DRAWSTRING` over `PRINT`
+- Wrap each frame's drawing in `SCREENLOCK ON` / `SCREENLOCK OFF`
+- Always use a function's return value  assign with `LET` or consume with `PRINT` or `IF`
+- If a feature isn't documented in this guide, say so rather than inventing one  BazzBasic does not silently inherit QBASIC, FreeBASIC, or VB conventions
+
+---
+
+
+## ABOUT
+BazzBasic is built around one simple idea: starting programming should feel nice and even fun. Ease of learning, comfort of exploration and small but important moments of success. Just like the classic BASICs of decades past, but with a fresh and modern feel.
+
+### What people have built with it
+
+BazzBasic is built for beginners, but it isn't a toy. It can carry real 2D games and even 2.5D graphics work.
+
+- https://github.com/EkBass/BazzBasic/blob/main/Examples/Voxel_terrain.bas
+A Comanche-style heightmap renderer with procedurally generated terrain. Eight smoothing passes turn random noise into hills, valleys, water, beaches, forests, rock, and snow  each assigned a color by height band.
+- https://github.com/EkBass/BazzBasic/blob/main/Examples/Raycaster_3d_optimized.bas
+A smooth first-person raycaster engine written entirely in BazzBasic. Minimap, depth shading and real-time movement  proves that BazzBasic can handle serious graphics work.
+- https://ek-bass.itch.io/rgb-vision
+A speedrun platformer made for Jam for All BASIC Dialects #7 (itch.io).
+- https://github.com/EkBass/BazzBasic/blob/main/Examples/2D_maze_FOV_demo_console.bas
+2D maze with FOV in your console
+- https://ek-bass.itch.io/eliza-bazzbasic-edition
+A classic DOCTOR script from the 60s which made people honestly believe they are talking to a real human. Grandmother of modern AIs.
+- https://github.com/EkBass/BazzBasic/blob/main/Examples/rosetta-code/BrainFuck.bas
+BrainFuck interpreter. One of the first programs ever done with BazzBasic.
+- https://github.com/EkBass/BazzBasic/blob/main/Examples/Anthropic_Claude_API_call.bas & https://github.com/EkBass/BazzBasic/blob/main/Examples/OpenAI_request.bas
+Anthropic Claude API and OpenAI ChatGPT API available, both with less than 50 lines of code.
+
+**Note:** All ".../Examples/..." codes are delivered with BazzBasic and they are found on the BazzBasic executable folder.
+
+### STORY
+Although over the years, as my own skills have grown, I have moved on to more versatile and modern languages, BASIC has always been something that has been fun to try out many different things with. Sometimes it's great to just make a simple adventure game again, a lottery machine, a quiz, or even just those balls bouncing on the screen. BazzBasic was created with this in mind. I wanted to create a language that makes it easy for you to give free rein to your curiosity and program something. And when you finish your first little game, you may crave something bigger and better. Maybe one day you will move on to another programming language, but then BazzBasic will have succeeded in doing what it was intended for.
+To arouse your curiosity.
+*EkBass*, author of BazzBasic
+
+---
+
+## Case sensitivity
+BazzBasic is not case-sensitive except with string contents.
+```basic
+let blaa$ = "Hello"
+PriNT BLAA$ ' output: Hello
+```
+
+---
+
+## Line Continuation
+
+BazzBasic has **no line-continuation character**. Do not generate `_` (VBA), `\` (Python), or `&` (other dialects). The lexer figures out continuation automatically using two rules.
+
+**Rule 1 operator at end of line.** If a line ends in a token that cannot legally end an expression, the next line continues it:
+
+```basic
+LET total$ = price$ * count$ -
+             discount$
+
+IF score$ >= 0 AND
+   score$ <= 100 THEN
+    PRINT "Valid"
+END IF
+
+LET counter$ +=
+    step$
+```
+
+Tokens that trigger this: `+ - * / % = <> < <= > >= AND OR += -= *= /= ,`
+
+> `MOD` is a function `MOD(a, b)`, not a binary operator  it does not trigger continuation. Use `%` for the modulo operator.
+
+**Rule 2  open paren.** Anything inside an unmatched `(` keeps reading until the matching `)`:
+
+```basic
+LET dist$ = DISTANCE(
+    x1$, y1$,
+    x2$, y2$
+)
+```
+
+Both rules combine:
+
+```basic
+LET total$ = (
+    base$ +
+    tax$
+)
+```
+
+**Trap for AI generators.** Do NOT emit a trailing `_`, `\`, `&`, or any other continuation marker  they are not BazzBasic syntax and will produce parse errors. Just leave the operator at the end of the line, or open a paren.
+
+---
+
+## Variables & Constants
+Variables and constants must be declared with LET before they can be used.  
+BazzBasic variables are not typed, but work the same way as in JavaScript, for example.  
+A variable needs the suffix $ which often is linked as STRING in traditional basic variants.  
+
+Variables require suffix "$". Constants require suffix "#".
+The suffix does not define data type  only "#" indicates immutability.
+```basic
+LET a$                      ' Declare variable without value
+LET b$, c$, d$				' Multiple variable declarations without value
+LET e$, f$ = "foo", g$ = 10	' Multiple variable declaration, e$ stays empty, f$ and g$ gets values
+
+LET name$ = "Alice"         ' String variable
+LET score$ = 0              ' Numeric variable
+
+LET PI# = 3.14159           ' Constant (immutable)
+LET TITLE# = "My Game"      ' String constant
+```
+
+**Compound assignment operators** (variables only  **not** allowed with `#` constants):
+
+```basic
+LET x$ = 1
+x$ += 5     ' add
+x$ -= 3     ' subtract
+x$ *= 2     ' multiply
+x$ /= 4     ' divide
+LET s$ = "Hello"
+s$ += " World"  ' string concatenation
+```
+
+**Scope:** All main-code variables share one scope (IF, FOR, and WHILE do NOT create new scope).  
+Main-code variables ($) are NOT accessible inside DEF FN  
+`DEF FN` functions are fully isolated  only global constants (`#`) accessible inside.
+
+**Comparison:** `"123" = 123` is TRUE (cross-type), but keep types consistent for speed.
+
+---
+
+### Built-in Constants
+- **Boolean:** `TRUE`, `FALSE`
+- **Math:** `PI#`, `HPI#` (PI#/2), `QPI#` (PI#/4), `TAU#` (PI# * 2), `EULER#` (e)  `#` suffix required
+- **System:** `PRG_ROOT#` (program base directory path)
+- **Keyboard:** `KEY_ESC#`, `KEY_ENTER#`, `KEY_SPACE#`, `KEY_UP#`, `KEY_DOWN#`, `KEY_LEFT#`, `KEY_RIGHT#`, `KEY_F1#`…`KEY_F12#`, `KEY_A#`…`KEY_Z#`, `KEY_0#`…`KEY_9#`, `KEY_LSHIFT#`, `KEY_LCTRL#`, etc.
+
+---
+
+## Arrays
+BazzBasic arrays are fully dynamic and support numeric, string, or mixed indexing.  
+
+
+```basic
+DIM scores$                         ' Declare (required before use)
+DIM a$, b$, c$                      ' Multiple
+scores$(0) = 95                     ' Numeric indices are 0-based.
+scores$("name") = "Alice"           ' String keys are associative and unordered.
+matrix$(0, 1) = "A2"                ' Multi-dimensional
+
+DIM sounds$
+    sounds$("guns", "shotgun_shoot")    = "shoot_shotgun.wav"
+    sounds$("guns", "shotgun_reload")   = "reload_shotgun.wav"
+    sounds$("guns", "ak47_shoot")       = "shoot_ak47.wav"
+    sounds$("guns", "ak47_reload")      = "reload_ak47.wav"
+    sounds$("food", "ham_eat")          = "eat_ham.wav"
+
+PRINT LEN(sounds$())        ' 5 as full size of arrayas there is total of 5 values in array
+PRINT ROWCOUNT(sounds$())   ' 2, "guns" & "food"
+```
+
+| Function/Command | Description |
+|-----------------|-------------|
+| `LEN(arr$())` | Total element count (LEN counts all nested elements across all dimensions) |
+| `ROWCOUNT(arr$())` | Count of first-dimension rows  use this for FOR loops over multi-dim arrays |
+| `HASKEY(arr$(key))` | 1 if exists, 0 if not |
+| `DELKEY arr$(key)` | Remove one element |
+| `DELARRAY arr$` | Remove entire array (can re-DIM after) |
+| `JOIN dest$, src1$, src2$` | Merge two arrays; `src2$` keys overwrite `src1$`. Use empty `src1$` as `COPYARRAY`. |
+
+**JOIN** Matching keys from src2$ overwrite src1$ at the same level
+
+**Always check with `HASKEY` before reading uninitialized elements.**
+
+---
+
+## Control Flow
+
+```basic
+' Block IF
+IF score$ >= 90 THEN
+    PRINT "A"
+ELSEIF score$ >= 80 THEN
+    PRINT "B"
+ELSE
+    PRINT "F"
+END IF                      ' ENDIF also works
+
+' One-line IF
+IF lives$ = 0 THEN GOTO [game_over]
+IF key$ = KEY_ESC# THEN GOTO [menu] ELSE GOTO [play]
+
+' FOR (auto-declares variable)
+FOR i$ = 1 TO 10 STEP 2 : PRINT i$ : NEXT
+FOR i$ = 10 TO 1 STEP -1 : PRINT i$ : NEXT
+
+' WHILE
+WHILE x$ < 100
+    x$ = x$ * 2
+WEND
+
+' Labels, GOTO, GOSUB
+[start]
+    GOSUB [sub:init]
+	' Avoid jumping into the middle of logical blocks (e.g. inside IF/WHILE)
+    GOTO [start]
+
+[sub:init]
+    LET x$ = 0
+RETURN
+
+' Dynamic jump (variable must contain "[label]" with brackets)
+LET target$ = "[menu]"
+GOTO target$
+
+' Other
+SLEEP 2000                  ' Pause for milliseconds
+END                         ' Terminate program
+```
+**Note:** Labels are case-insensitive and may contain almost any printable character.
+Whitespace is trimmed. Everything between "[" and "]" is treated as the label name.
+---
+
+## I/O
+
+| Command | Description |
+|---------|-------------|
+| `PRINT expr; expr` | `;` = no space, `,` = tab |
+| `PRINT "text";` | Trailing `;` suppresses newline |
+| `INPUT "prompt", var$` | Splits on whitespace/comma |
+| `INPUT "prompt", a$, b$` | Multiple values |
+| `LINE INPUT "prompt", var$` | Read entire line with spaces |
+| `CLS` | Clear screen |
+| `LOCATE row, col` | Move cursor (1-based) |
+| `CURPOS("row")` / `CURPOS("col")` | Read cursor row or col (1-based, matches LOCATE) |
+| `CURPOS()` | Read cursor as `"row,col"` string |
+| `COLOR fg, bg` | Text colors (0-15 palette) |
+| `SHELL("cmd")` | Run shell command, returns output |
+| `SHELL("cmd", ms)` | With timeout in ms (default 5000) |
+
+' ; prints without spacing
+' , prints tab separation
+' Both can be mixed in a single PRINT statement
+' INPUT splits on whitespace and comma; quoted strings are treated as single values
+
+**Escape sequences in strings:** `\"` `\n` `\t` `\\`
+
+**SHELL + SQLite.** SQLite (the `sqlite3` CLI tool) is the recommended way to add a real database to a BazzBasic script — see the *SQLite Database* page in the manual for the full guide. Three things to remember when generating SHELL commands that wrap SQL:
+- Always append `2>&1` to the command, or SQL errors disappear silently.
+- Use `\"` (BazzBasic escape) to wrap the SQL for the OS shell: `SHELL("sqlite3 db.sqlite \"SELECT * FROM users\" 2>&1")`.
+- In paths use `/` or `\\` — never a single `\`.
+
+### Keyboard Input
+| Function | Returns | Notes |
+|----------|---------|-------|
+| `INKEY` | Key value or 0 | Non-blocking |
+| `KEYDOWN(key#)` | TRUE/FALSE | Held-key detection; KEYDOWN only works in graphics mode |
+| `WAITKEY(key#, ...)` | Key value | Blocks until key pressed; `WAITKEY()` = any key |
+
+### Mouse (graphics mode only)
+`MOUSEX`, `MOUSEY`  cursor position  
+`MOUSELEFT`, MOUSERIGHT, MOUSEMIDDLE  return 1 if pressed, 0 otherwise  
+`MOUSEHIDE`  hide the mouse cursor (graphics screen only)  
+`MOUSESHOW`  restore the mouse cursor (graphics screen only)
+
+### Console Read
+Returns numeric or character depending on type parameter  
+`GETCONSOLE(row, col, type)`  type: 0=char (ASCII), 1=fg color, 2=bg color
+
+---
+
+## User-Defined Functions
+
+```basic
+' Define BEFORE calling. Name must end with $.
+DEF FN Clamp$(val$, lo$, hi$)
+    IF val$ < lo$ THEN RETURN lo$
+    IF val$ > hi$ THEN RETURN hi$
+    RETURN val$
+END DEF
+
+PRINT FN Clamp$(5, 1, 10)          '  OK  return value used
+LET v$ = FN Clamp$(15, 0, 10)     '  OK
+FN Clamp$(5, 1, 10)                '  ERROR  return value unused
+' Return value must be assigned with LET or consumed by PRINT  there is no way to silently discard it.
+```
+
+- Isolated scope: no access to global variables, only global constants (`#`)
+- Parameters passed **by value**
+- Labels inside functions are local  GOTO/GOSUB cannot jump outside
+- Supports recursion
+- Arrays as parameters not allowed. Use ASJSON to make array as JSON-string to pass it.
+- Use `INCLUDE` to load functions from separate files if many
+
+---
+
+## String Functions
+
+| Function | Description |
+|----------|-------------|
+| `ASC(s$)` | ASCII code of first char |
+| `CHR(n)` | Character from ASCII code |
+| `FSTRING(template$)` | String interpolation with `{{-name-}}` placeholders. See dedicated FSTRING section below for full syntax. |
+| `INSTR(s$, search$)` | Position (1-based), 0=not found; case-sensitive by default |
+| `INSTR(s$, search$, mode)` | mode: 0=case-insensitive, 1=case-sensitive |
+| `INSTR(start, s$, search$)` | Search from position (case-sensitive) |
+| `INVERT(s$)` | Reverse string |
+| `LCASE(s$)` / `UCASE(s$)` | Lower / upper case |
+| `LEFT(s$, n)` / `RIGHT(s$, n)` | First/last n chars |
+| `LEN(s$)` | String length |
+| `LTRIM(s$)` / `RTRIM(s$)` / `TRIM(s$)` | Strip whitespace |
+| `MID(s$, start)` | Substring from start (1-based) |
+| `MID(s$, start, len)` | Substring with length |
+| `REPEAT(s$, n)` | Repeat string n times |
+| `REPLACE(s$, a$, b$)` | Replace a$ with b$ in s$ |
+| `SPLIT(arr$, s$, sep$)` | Split into array, returns count. Expects array is declared with DIM |
+| `SRAND(n)` | Random alphanumeric string of length n |
+| `STR(n)` | Number to string |
+| `VAL(s$)` | String to number |
+| `SHA256(s$)` | SHA256 hash (64-char hex) |
+| `BASE64ENCODE(s$)` / `BASE64DECODE(s$)` | Base64 encode/decode |
+
+---
+
+## FSTRING - String Interpolation
+
+`FSTRING(template$)` substitutes `{{-name-}}` placeholders inside a template
+string with the value of variables, constants, or array elements. It is the
+recommended alternative to long `+` concatenation chains.
+
+```basic
+LET name$ = "Krisu"
+LET LEVEL# = 5
+PRINT FSTRING("Hello {{-name$-}}, level {{-LEVEL#-}}")
+' Output: Hello Krisu, level 5
+```
+
+### Why the `{{-...-}}` markers?
+
+The triple-character markers `{{-` and `-}}` are deliberately unusual so they
+will not collide with normal text inside a string. There is no escape syntax;
+if a template contains literal `{{-...-}}`, FSTRING will always try to resolve
+it as a placeholder.
+
+### Placeholder forms
+
+| Form | Resolves to |
+|------|-------------|
+| `{{-var$-}}` | Value of variable `var$` |
+| `{{-CONST#-}}` | Value of constant `CONST#` |
+| `{{-arr$(0)-}}` | Array element at numeric index `0` |
+| `{{-arr$(i$)-}}` | Array element at index taken from variable `i$` |
+| `{{-arr$(KEY#)-}}` | Array element at index taken from constant `KEY#` |
+| `{{-arr$(name)-}}` | Array element at literal string key `"name"` (no quotes inside FSTRING) |
+| `{{-arr$(0, i$)-}}` | Multidimensional element, mixed literal and variable indices |
+
+### Index resolution rule (for array access)
+
+For each comma-separated index, FSTRING decides what it is by looking at the
+last character:
+
+1. Ends with `$` or `#` -> treat as variable / constant lookup. Halts with an
+   error if the name is not defined.
+2. Parses as a number (`0`, `1.5`, `-3`) -> treat as a numeric index. The
+   number is normalised through a double round-trip so `arr$(01)` and
+   `arr$(1.0)` both find the key `1`.
+3. Otherwise -> treat as a literal string key. This is what lets you write
+   `{{-player$(name)-}}` to read what was stored with `player$("name") = ...`.
+
+### Whitespace inside placeholders
+
+All whitespace inside a placeholder is trimmed, so these are equivalent:
+
+```basic
+FSTRING("{{-name$-}}")
+FSTRING("{{- name$ -}}")
+FSTRING("{{-  name$  -}}")
+FSTRING("{{- arr$( 0 , i$ ) -}}")
+```
+
+### Numbers auto-stringify
+
+Both numeric variables / constants and array elements that hold numbers are
+converted to strings automatically (no `STR()` needed):
+
+```basic
+LET score$ = 42
+LET pi#    = 3.14159
+PRINT FSTRING("Score: {{-score$-}}, Pi: {{-pi#-}}")
+' Output: Score: 42, Pi: 3.14159
+```
+
+### What is NOT supported (intentional)
+
+These are out of scope; FSTRING is meant to stay simple and predictable. Use
+a normal variable to pre-compute, then reference that variable in FSTRING.
+
+```basic
+' WRONG: arithmetic inside placeholder
+PRINT FSTRING("Total: {{-a$ + 5-}}")
+
+' WRONG: function call inside placeholder
+PRINT FSTRING("Name: {{-UCASE(name$)-}}")
+
+' WRONG: nested array lookup inside placeholder
+PRINT FSTRING("{{-arr$(arr2$(0))-}}")
+
+' WRONG: string literal with quotes inside placeholder
+PRINT FSTRING("{{-arr$(\"name\")-}}")
+```
+
+```basic
+' RIGHT: pre-compute, then reference
+LET total$ = a$ + 5
+LET upper$ = UCASE(name$)
+LET k$     = arr2$(0)
+PRINT FSTRING("Total: {{-total$-}}, Name: {{-upper$-}}, Item: {{-arr$(k$)-}}")
+```
+
+### Errors halt execution
+
+Like other BazzBasic errors, these print a line-numbered message and stop
+the program:
+
+- `FSTRING: undefined variable 'foo$'.`
+- `FSTRING: undefined variable 'i$' in array index of 'arr$(i$)'.`
+- `FSTRING: missing closing '-}}' in template.`
+- `FSTRING: empty placeholder '{{--}}'.`
+- `FSTRING: malformed array access '...'.`
+- `FSTRING: Array element ...(...) not initialized` (the standard array error,
+  prefixed with FSTRING).
+
+### Common AI mistakes with FSTRING
+
+```basic
+' WRONG: forgot the dashes
+LET s$ = FSTRING("Hi {{name$}}")
+
+' WRONG: only one brace pair
+LET s$ = FSTRING("Hi {-name$-}")
+
+' WRONG: $ suffix omitted in placeholder
+LET s$ = FSTRING("Hi {{-name-}}")
+' This compiles but treats `name` as a literal key for an array lookup.
+' If `name` is intended as a variable, write `{{-name$-}}`.
+
+' WRONG: using FSTRING as a statement
+FSTRING("Hi {{-name$-}}")
+' FSTRING returns a value; you must use it: LET / PRINT / pass to function.
+
+' RIGHT
+LET s$ = FSTRING("Hi {{-name$-}}, level {{-LEVEL#-}}")
+PRINT FSTRING("Score: {{-score$-}}")
+```
+
+### Full working example
+
+```basic
+DIM player$
+    player$("name")  = "Krisu"
+    player$("class") = "Bass"
+    player$("level") = 99
+
+DIM grid$
+    grid$(0, 0) = "X"
+    grid$(0, 1) = "O"
+    grid$(1, 0) = "."
+    grid$(1, 1) = "X"
+
+LET row$ = 1
+LET PI# = 3.14
+
+PRINT FSTRING("{{-player$(name)-}} the {{-player$(class)-}}, lvl {{-player$(level)-}}")
+PRINT FSTRING("Row {{-row$-}}: [{{-grid$(row$, 0)-}}{{-grid$(row$, 1)-}}]")
+PRINT FSTRING("Pi is roughly {{-PI#-}}")
+END
+```
+
+Output:
+```
+Krisu the Bass, lvl 99
+Row 1: [.X]
+Pi is roughly 3.14
+```
+
+---
+
+## Math Functions
+
+| Function | Description |
+|----------|-------------|
+| `ABS(n)` | Absolute value |
+| `ATAN(n)` | Arc tangent |
+| `ATAN2(x, y)` | Returns the angle, in radians, between the positive x-axis and a vector to the point with the given (x, y) coordinates in the Cartesian plane |
+| `BETWEEN(n, min, max)` | TRUE if min ≤ n ≤ max |
+| `INBETWEEN(n, min, max)` | TRUE if min < n < max (strictly between, not equal) |
+| `CEIL(n)` / `FLOOR(n)` | Round up / down |
+| `CINT(n)` | Round to nearest integer |
+| `CLAMP(n, min, max)` | Constrain n to [min, max] |
+| `COS(n)` / `SIN(n)` / `TAN(n)` | Trig (radians) |
+| `DEG(rad)` / `RAD(deg)` | Radians ↔ degrees |
+| `DISTANCE(x1,y1, x2,y2)` | 2D Euclidean distance |
+| `DISTANCE(x1,y1,z1, x2,y2,z2)` | 3D Euclidean distance |
+| `EXP(n)` | e^n |
+| `INT(n)` | Truncate toward zero |
+| `LERP(start, end, t)` | Linear interpolation (t: 0.0–1.0) |
+| `LOG(n)` | Natural logarithm |
+| `MAX(a, b)` / `MIN(a, b)` | Larger / smaller of two |
+| `MOD(a, b)` | Remainder |
+| `POW(base, exp)` | Power |
+| `RND(n)` | Random integer 0 to n-1 if n > 0 |
+| `RND(0)` | Float between 0.0 and 1.0 (IE: 0.5841907423666761) |
+| `ROUND(n)` | Standard rounding |
+| `SGN(n)` | Sign: -1, 0, or 1 |
+| `SQR(n)` | Square root |
+
+**Math constants:** `PI#`, `HPI#` (PI/2), `QPI#` (PI/4), `TAU#` (PI*2), `EULER#`
+
+---
+
+## Variable Functions
+
+| Function | Description |
+|----------|-------------|
+| `ISSET(name)` | `1` if the named variable (`$`) or constant (`#`) is declared, `0` otherwise. Argument is **not evaluated**  `ISSET(undef$)` safely returns `0`. |
+
+`ISSET` is the only language-introspection function and it has tight rules:
+
+- **Scalars only.** Variables (`$`) and constants (`#`). Arrays and array
+  elements are stored separately  `ISSET(arr$)` and `ISSET(arr$(0))` always
+  return `0`, never an error.
+- **Bare name only.** No expressions, no string literals, no numbers. These
+  all error with "invalid parameter":
+  ```basic
+  ISSET(a$ + b$)   ' WRONG: expression
+  ISSET("a$")      ' WRONG: string literal
+  ISSET(42)        ' WRONG: number
+  ISSET()          ' WRONG: empty
+  ```
+- **Suffix is part of the name.** `a$` and `A#` are different names:
+  ```basic
+  LET a$ = "foo"
+  PRINT ISSET(a$)  ' 1
+  PRINT ISSET(A#)  ' 0
+  ```
+- **`LET name$` (no value) still counts as set.** `LET` always registers the
+  variable; the value just defaults to empty string for `$` and zero for
+  numeric. `ISSET` reports declaration, not "has a meaningful value".
+
+Typical use is guarding optional setup:
+
+```basic
+IF NOT ISSET(playerName$) THEN
+    LET playerName$ = "Anonymous"
+END IF
+```
+
+---
+
+## Graphics
+
+```basic
+SCREEN 12                           ' 640×480 VGA
+SCREEN 0, 800, 600                  ' Custom size
+SCREEN 0, 1024, 768, "My Game"      ' Custom size + title
+FULLSCREEN TRUE                     ' Borderless fullscreen (graphics only)
+FULLSCREEN FALSE                    ' Windowed
+```
+
+| Mode | Resolution |
+|------|-----------|
+| 1 | 320×200 |
+| 2 | 640×350 |
+| 7 | 320×200 |
+| 9 | 640×350 |
+| 12 | 640×480 ← recommended |
+| 13 | 320×200 |
+
+### Drawing Primitives
+```basic
+PSET (x, y), color							' Pixel
+LINE (x1,y1)-(x2,y2), color                	' Line
+LINE (x1,y1)-(x2,y2), color, B             	' Box outline
+LINE (x1,y1)-(x2,y2), color, BF            	' Box filled (FAST  use instead of CLS)
+CIRCLE (cx,cy), radius, color              	' Circle outline
+CIRCLE (cx,cy), radius, color, 1           	' Circle filled
+PAINT (x, y), fillColor, borderColor       	' Flood fill
+LET c$ = POINT(x, y)                       	' Read pixel color
+LET col$ = RGB(r, g, b)                    	' Create color (0–255 each)
+```
+
+**Color palette (COLOR command, 0–15):** 0=Black, 1=Blue, 2=Green, 3=Cyan, 4=Red, 5=Magenta, 6=Brown, 7=Lt Gray, 8=Dk Gray, 9=Lt Blue, 10=Lt Green, 11=Lt Cyan, 12=Lt Red, 13=Lt Magenta, 14=Yellow, 15=White
+
+### Screen Control
+```basic
+SCREENLOCK ON                       ' Buffer drawing (start frame)
+SCREENLOCK OFF                      ' Present buffer (end frame)
+VSYNC(TRUE)                         ' Enable VSync (default, ~60 FPS)
+VSYNC(FALSE)                        ' Disable VSync (benchmarking)
+CLS                                 ' Clear screen
+' Use CLS only with console, in graphics screen its slow
+' With graphics screen, prefer LINE BF
+```
+
+### Shapes & Images
+```basic
+' Create shape
+' LOADSHAPE and LOADIMAGE return a stable integer handle  never reassigned.
+' SDL2 owns the resource; your code only ever holds this one reference. Use constants.
+LET RECT# = LOADSHAPE("RECTANGLE", w, h, color)  ' or "CIRCLE", "TRIANGLE"
+LET IMG_PLAYER# = LOADIMAGE("player.png")         ' PNG (alpha) or BMP
+LET IMG_REMOTE# = LOADIMAGE("https://example.com/a.png") ' Download + load
+
+' Sprite sheet  sprites indexed 1-based
+DIM sprites$
+LOADSHEET sprites$, 128, 128, "sheet.png"        ' tileW, tileH, file
+MOVESHAPE sprites$(1), x, y                      ' sprites$(1) = first sprite
+
+' Transform
+MOVESHAPE RECT#, x, y               ' Position by center point
+ROTATESHAPE RECT#, angle            ' Degrees (absolute)
+SCALESHAPE RECT#, scale             ' 1.0 = original size
+DRAWSHAPE RECT#                     ' Render to buffer
+SHOWSHAPE RECT# / HIDESHAPE RECT#   ' Toggle visibility
+REMOVESHAPE RECT#                   ' Free memory (always clean up)
+```
+
+
+---
+
+### Text Rendering (SDL2_ttf.dll required)
+#### DRAWSTRING & LOADFONT
+
+
+```basic
+' Default font (Arial)
+DRAWSTRING "Hello!", 100, 200, RGB(255, 255, 255)
+
+' Load alternative font  becomes the new default
+LOADFONT "comic.ttf", 24
+DRAWSTRING "Hello!", 100, 200, RGB(255, 255, 255)
+
+' Reset to Arial
+LOADFONT
+```
+
+`DRAWSTRING x, y` positions the top-left of the text. Requires `SDL2_ttf.dll` in the same directory as the interpreter. Prefer this over PRINT, which makes graphic screen easily blinking.
+
+---
+
+## Sound
+
+```basic
+' LOADSOUND returns a stable integer handle  SDL2 manages the resource.
+' The handle never changes; store it in a constant to protect it from accidental reassignment.
+LET SND_JUMP# = LOADSOUND("jump.wav")   ' Load (WAV recommended)
+SOUNDONCE(SND_JUMP#)                    ' Play once, non-blocking
+SOUNDONCEWAIT(SND_JUMP#)               ' Play once, wait for finish
+SOUNDREPEAT(SND_JUMP#)                 ' Loop continuously
+SOUNDSTOP(SND_JUMP#)                   ' Stop specific sound
+SOUNDSTOPALL                            ' Stop all sounds
+```
+
+Load all sounds at startup. Call `SOUNDSTOPALL` before `END`.
+
+---
+
+## File I/O
+
+```basic
+LET data$ = FileRead("file.txt")        ' Read as string
+DIM cfg$ : LET cfg$ = FileRead("settings.txt")  ' Read as key=value array
+FILEWRITE "save.txt", data$             ' Create/overwrite
+FILEAPPEND "log.txt", entry$            ' Append
+LET ok$ = FILEEXISTS("file.txt")        ' 1=exists, 0=not
+FILEDELETE "temp.dat"                   ' Delete file
+```
+
+**key=value parsing:** When `FileRead` assigns to a `DIM`'d array, lines `key=value` become `arr$("key")`. Lines starting with `#` are comments. Perfect for `.env` files.
+
+```basic
+DIM env$
+LET env$ = FileRead(".env")
+LET API_KEY# = env$("OPENAI_API_KEY")
+```
+
+**Paths:** Use `/` or `\\`  never single `\` (it's an escape char). Relative paths are from `PRG_ROOT#`.  
+**FileWrite with array** saves in key=value format (round-trips with FileRead).
+
+---
+
+## Network
+
+```basic
+LET res$ = HTTPGET("https://api.example.com/data")
+LET res$ = HTTPPOST("https://api.example.com/submit", "{""key"":""val""}")
+
+' With headers (optional last parameter)
+DIM headers$
+headers$("Authorization") = "Bearer mytoken"
+headers$("Content-Type") = "application/json"
+LET res$ = HTTPGET("https://api.example.com/data", headers$)
+LET res$ = HTTPPOST("https://api.example.com/data", body$, headers$)
+```
+
+### Local HTTP server (LISTEN)
+
+BazzBasic can also receive requests as a local-only HTTP server, typically used as glue between a static HTML page and a BazzBasic script on the same machine.
+
+```basic
+STARTLISTEN 8080                       ' bind 127.0.0.1:8080, no admin needed
+STARTLISTEN 8080, 5000                 ' optional timeout in ms
+LET body$ = GETREQUEST()               ' POST/PUT/PATCH body, or GET query string ("" on timeout)
+SENDRESPONSE "{""status"":""ok""}"     ' must be called or browser hangs
+STOPLISTEN
+```
+
+Important rules:
+
+- **Always pair `GETREQUEST()` with `SENDRESPONSE`.** The browser is waiting on the response. Forgetting `SENDRESPONSE` makes the page hang.
+- **Bound to `127.0.0.1` only.** This is local glue, not a real web server. Do not generate code that tries to expose this on the LAN or internet.
+- **Body or query string, not full request.** `GETREQUEST()` returns just the POST body (or the GET query string without `?`). Headers, method, and URL path are NOT exposed in this version. If you need structured data, parse the body with `ASARRAY(body$)`.
+- **OPTIONS preflight is automatic.** Do NOT write code that handles `OPTIONS`  it is consumed silently and never reaches user code.
+- **CORS is automatic.** Every response carries `Access-Control-Allow-Origin: *`. No need to set it manually.
+- **One listener at a time.** Calling `STARTLISTEN` while one is already active is an error. Call `STOPLISTEN` first.
+- **Always 200 OK, always `text/plain`.** Custom status codes and content types are not supported in this version. To return JSON, just put JSON text in the body  browser-side `response.json()` still works.
+
+Typical receive-and-process pattern:
+
+```basic
+STARTLISTEN 8080
+PRINT "Waiting for browser..."
+
+LET json$ = GETREQUEST()
+DIM data$
+LET data$ = ASARRAY(json$)
+
+PRINT "Got name: " + data$("name")
+
+SENDRESPONSE "{""status"":""ok""}"
+STOPLISTEN
+END
+```
+
+---
+
+## Arrays & JSON
+
+Nested JSON maps to comma-separated keys: `data$("player,name")`, `data$("skills,0")`
+
+```basic
+' Array → JSON string
+LET json$ = ASJSON(arr$)
+
+' JSON string → array (returns element count)
+DIM data$
+LET count$ = ASARRAY(data$, json$)
+
+' Load/save JSON files
+LOADJSON arr$, "file.json"
+SAVEJSON arr$, "file.json"
+```
+
+---
+
+## Fast Trigonometry
+
+~20× faster than `SIN(RAD(x))`, 1-degree (integer) precision. Uses ~5.6 KB memory.
+
+```basic
+FastTrig(TRUE)                      ' Enable lookup tables (must call first)
+LET x$ = FastCos(45)               ' Degrees, auto-normalized 0–359
+LET y$ = FastSin(90)
+LET r$ = FastRad(180)              ' Deg→rad (no FastTrig needed)
+FastTrig(FALSE)                     ' Free memory
+```
+
+Use for raycasting, sprite rotation, particle systems, any high-freq trig.
+
+---
+
+## Command-Line Arguments
+
+```basic
+' bazzbasic.exe myprog.bas arg1 arg2
+PRINT ARGCOUNT         ' number of args (2 in this example)
+PRINT ARGS(0)          ' first arg  → "arg1"
+PRINT ARGS(1)          ' second arg → "arg2"
+```
+
+`ARGCOUNT` and `ARGS(n)` are 0-based; ARGS does not include the interpreter or script name.
+
+---
+
+## Libraries & INCLUDE
+
+```basic
+INCLUDE "helpers.bas"               ' Insert source at this point
+INCLUDE "MathLib.bb"                ' Load compiled library
+
+' Compile library (functions only  no loose code)
+' bazzbasic.exe -lib MathLib.bas  →  MathLib.bb
+' Function names auto-prefixed: MATHLIB_functionname$
+PRINT FN MATHLIB_add$(5, 3)
+```
+
+Library functions can read main-program constants (`#`). `.bb` files are version-locked.
+
+---
+
+## Passing Arrays to Functions
+
+Arrays cannot be passed directly to `DEF FN` functions, but a clean workaround exists using JSON serialization. Convert the array to a JSON string with `ASJSON`, pass the string as a parameter, then deserialize inside the function with `ASARRAY`. This is the accepted pattern in BazzBasic v1.2+.
+
+```basic
+DEF FN ProcessPlayer$(data$)
+    DIM arr$
+    LET count$ = ASARRAY(arr$, data$)
+    RETURN arr$("name") + " score:" + arr$("score")
+END DEF
+
+[inits]
+    DIM player$
+    player$("name") = "Alice"
+    player$("score") = 9999
+    player$("address,city") = "New York"
+
+[main]
+    LET json$ = ASJSON(player$)
+    PRINT FN ProcessPlayer$(json$)
+END
+```
+
+**Notes:**
+- The function receives a full independent copy  changes inside do not affect the original array
+- Nested keys work normally: `arr$("address,city")` etc.
+- Overhead is similar to copying an array manually; acceptable for most use cases
+
+---
+
+## Program Structure
+
+```basic
+' ---- 1. FUNCTIONS (or INCLUDE "functions.bas/bb") ----
+DEF FN Clamp$(v$, lo$, hi$)
+    IF v$ < lo$ THEN RETURN lo$
+    IF v$ > hi$ THEN RETURN hi$
+    RETURN v$
+END DEF
+
+' ---- 2. INIT (declare ALL constants & variables here, not inside loops) ----
+' Performance: variables declared outside loops avoid repeated existence checks.
+[inits]
+	LET SCREEN_W# = 640
+	LET SCREEN_H# = 480
+	LET MAX_SPEED# = 5
+
+    SCREEN 0, SCREEN_W#, SCREEN_H#, "My Game"
+
+    LET x$ = 320
+    LET y$ = 240
+    LET running$ = TRUE
+
+' ---- 3. MAIN LOOP ----
+[main]
+    WHILE running$
+        IF INKEY = KEY_ESC# THEN running$ = FALSE
+        GOSUB [sub:update]
+        GOSUB [sub:draw]
+        SLEEP 16
+    WEND
+    SOUNDSTOPALL
+END ' place at the end of main program so BazzBasic wont fall to subs in runtime
+
+' ---- 4. SUBROUTINES (or INCLUDE "subs.bas") ----
+[sub:update]
+    IF KEYDOWN(KEY_LEFT#)  THEN x$ = x$ - MAX_SPEED#
+    IF KEYDOWN(KEY_RIGHT#) THEN x$ = x$ + MAX_SPEED#
+RETURN
+
+[sub:draw]
+    SCREENLOCK ON
+    LINE (0,0)-(SCREEN_W#, SCREEN_H#), 0, BF
+    CIRCLE (x$, y$), 10, RGB(0, 255, 0), 1
+    SCREENLOCK OFF
+RETURN
+```
+
+**Key conventions:**
+- Variables: `camelCase$` | Constants: `UPPER_SNAKE_CASE#` | Functions: `PascalCase$`
+- Labels: `[gameLoop]` for jump targets, `[sub:name]` for subroutines
+- Image/sound/shape IDs are stable integer handles  **always** store as constants: `LET MY_IMG# = LOADIMAGE("x.png")`  never use `$` variables for these
+- Group many IDs → use arrays: `DIM sprites$` / `sprites$("player") = LOADIMAGE(...)`  but prefer named constants when count is small
+
+---
+
+## Performance Tips
+
+- `LINE (0,0)-(W,H), 0, BF` to clear  much faster than `CLS`
+- Always wrap draw code in `SCREENLOCK ON` / `SCREENLOCK OFF`
+- Store `RGB()` results in constants/variables  don't call RGB in hot loops
+- Declare all variables in `[inits]`, not inside loops or subroutines
+- Use `FastTrig` for any loop calling trig hundreds of times per frame
+- `SLEEP 16` in game loop → ~60 FPS
+
+---
+
+## Known Limitations
+
+Things to be aware of  most are deliberate design decisions, a few are practical constraints.
+
+- **Platform: Windows x64 only.** Linux and macOS are not supported. Browser/Android are not feasible  the runtime depends on SDL2 via P/Invoke.
+- **Arrays cannot be passed to functions.** Use the `ASJSON` / `ASARRAY` round-trip pattern. The function receives an independent copy.
+- **`DEF FN` scope is fully isolated.** Functions can read global `#` constants but cannot see any `$` variables from the outer scope. Pass values as parameters.
+- **No block scope.** `IF`, `FOR`, and `WHILE` do not create new variable scopes  all main-code variables share one namespace.
+- **No exception handling.** There is no `TRY`/`CATCH` and no `ON ERROR`. Runtime errors halt the program with a line-numbered message printed to the console.
+- **Division by zero returns `0` silently.** No exception, no warning. Guard with `IF b$ = 0 THEN ...` when correctness matters.
+- **No integer-division operator.** Use `INT(a / b)`, `FLOOR(a / b)`, or `CINT(a / b)` depending on the rounding behavior you need.
+- **Compiled `.bb` libraries are version-locked** to the BazzBasic build that produced them. Recompile after upgrading the interpreter.
+- **`DEF FN` definitions must precede their first call** in source order. Forward references don't resolve.
+
+---
+
+## IDE Features (v1.3)
+
+### New File Template
+When the IDE opens with no file (or a new file), this template is auto-inserted:
+```basic
+' BazzBasic version {ver_num}
+' https://ekbass.github.io/BazzBasic/
+```
+
+### Beginner's Guide
+- **IDE:** Menu → **Help** → **Beginner's Guide**  opens `https://github.com/EkBass/BazzBasic-Beginners-Guide/releases` in default browser
+- **CLI:** `bazzbasic.exe -guide` or `bazzbasic.exe -help`  prints URL to terminal
+
+### Check for Updates
+- **IDE:** Menu → **Help** → **Check for updated...**  IDE reports if a newer version is available
+- **CLI:** `bazzbasic.exe -checkupdate`
+
+### Compile via IDE
+- **Menu → Run → Compile as Exe**  compiles open file to standalone `.exe` (auto-saves first)
+- **Menu → Run → Compile as Library (.bb)**  compiles open file as reusable `.bb` library (auto-saves first)
+
+EOF