Add README.

README.md

@@ -1,22 +1,64 @@
 # chalk
 
-TODO: Write a description here
+Chalk is a basic compiler from a toy language into CHIP-8 bytecode.
+It supports some higher-level constructs like looks and if-statements,
+and has some higher-level functions for drawing numbers and sprites.
 
 ## Installation
 
-TODO: Write installation instructions here
+To compile chalk, simply run
+```Bash
+crystal build --release src/chalk.cr
+```
 
 ## Usage
+### Syntax
+Chalk has minimal syntax. All code goes into functions, which are declared as follows:
+```
+fun function(param, another_param): return_type {
 
-TODO: Write usage instructions here
+}
+```
+All parameters are assumed to be of type `u8`, an unsigned byte.
+The return type can be either `u8` or `u0`, the latter being the same as `void` in C.
+Users can declare variables using the `var` keyword:
+```
+var name = 5;
+```
+Assigning to existing variables is performed as such:
+```
+name = 6;
+```
+It's possible to call another function, which uses the CHIP-8 stack. This stack
+is used exclusively for function calls, and may not exceed 12, as per the specifications
+of the CHIP-8 virtual machine.
+```
+var result = double(name);
+```
+Additionally, to ensure that user-defined variables stored
+in registers are not modified, chalk uses its own custom stack, placed at the end of the program.
+This stack is accessed by modifying a stack pointer register, which holds the offset from the beginning of the stack. Because CHIP-8 registers can only hold up 8-bit unsinged numbers, the stack is therefore limited to 254 items.
 
-## Development
+If statements take "truthy" values to be those that have a nonzero value. As such,
+`if (0) {}` will never run, while `while(5) {}` will never terminate. Input can be awaited
+using the `get_key` function, which returns the number of the next key pressed.
 
-TODO: Write development instructions here
+Sprites can be declared using a quasi-visual syntax:
+```
+sprite dum [
+`  x  x  `
+`  x  x  `
+`  x  x  `
+`        `
+`x      x`
+` xxxxxx `
+]
+```
+These sprites can then be used in calls to `draw_sprite(sprite, x, y)`.
 
 ## Contributing
 
-1. Fork it (<https://github.com/your-github-user/chalk/fork>)
+1. Fork it (<https://github.com/DanilaFe/chalk/fork>)
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Commit your changes (`git commit -am 'Add some feature'`)
 4. Push to the branch (`git push origin my-new-feature`)
@@ -24,4 +66,4 @@ TODO: Write development instructions here
 
 ## Contributors
 
-- [your-github-user](https://github.com/your-github-user) Danila Fedorin - creator, maintainer
+- [DanilaFe](https://github.com/DanilaFe) Danila Fedorin - creator, maintainer