elaborate on what the debug repl can do

Author: wade-cheng

wiki/pygbag-debug/README.md

@@ -1,8 +1,39 @@
-For using repl and debugging pygbag games
-just use http://localhost:8000/#debug instead of just http://localhost:8000
+pygbag comes with an interactive Python-like REPL that can be used for debugging. 
+
+## to open
+To open the REPL, visit `http://localhost:8000/#debug` instead of just `http://localhost:8000`.
+
+To get debugger at runtime, open the [javascript console](https://developer.mozilla.org/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools#the_javascript_console) and run `debug()` by typing in `debug()` followed by pressing enter.
+
+## to use
+The REPL is a Python REPL that has loaded the project. This means if your pygbag main file includes a `main() function`, calling `type(main)` will return `<class 'function'>` instead of a `NameError`.
+
+It also implements a variety of shell-like commands, defined in the [shell](https://github.com/pygame-web/pygbag/blob/72b34546e23086c78f5b193c05e3e961b807f214/src/pygbag/support/cpythonrc.py#L266) class, that are reminiscent of shell languages common on Linux systems. These can be used in the REPL.
+For example,
+```bash
+>>> cat main.py
+```
+will dump the binary contents of `main.py` into the REPL, if `main.py` exists in your pygbag project directory. 
+
+Other helpful commands are available. For example,`rx` takes a list of files and downloads them from the browser's filesystem to a user's filesystem. For example,
+```bash
+>>> rx main.py assets/image.png assets/otherimage.png
+```
+will try to download the given three files.
+
+## Python versus browser logging
+`print` statements will write to this REPL instead of the browser's console.
+
+To write to the browser's console instead, use `platform.console.log`. For example,
+```py
+import sys, platform
+if sys.platform == "emscripten":
+    platform.console.log("logged message")
+```
+
+
+
 
-to get debugger at runtime use ctrl+shift+i to pop up javascript console from pygbag page tab and type : debug()
-followed by enter.
 
 
 [edit this page](https://github.com/pygame-web/pygame-web.github.io/edit/main/wiki/pygbag-debug/README.md)