diff --git a/md/learn/adts/union-types.md b/md/learn/adts/union-types.md
index ae653b0..b66dc7b 100644
--- a/md/learn/adts/union-types.md
+++ b/md/learn/adts/union-types.md
@@ -11,7 +11,7 @@ enum Suit
     Spades,
 }
 
-val suit = Suit::Hearts
+let suit = Suit::Hearts
 ```
 
 
@@ -24,7 +24,7 @@ enum IpAddress
     V6(String),
 }
 
-val addr_1 = IpAddress::V4("192.168.0.1")
+let addr_1 = IpAddress::V4("192.168.0.1")
 
 match addr_1
 | IpAddress::V4(ip)
diff --git a/md/learn/basics/variables.md b/md/learn/basics/variables.md
index a9906b6..656b37d 100644
--- a/md/learn/basics/variables.md
+++ b/md/learn/basics/variables.md
@@ -2,46 +2,25 @@
 
 thp distinguishes between mutable and immutable variables.
 
-## Mutable variables
-
-Defined with `var`, followed by a variable name and a value.
-
-```thp
-var name = "John"
-var age = 32
-```
-
-### Datatype annotation
-
-Written after the `var` keyword but before the variable name.
-
-```thp
-var String name = "John"
-var Int age = 32
-```
-
-When annotating a mutable variable the keyword `var` is _required_.
-
-
 ## Immutable variables
 
-Defined with `val`, followed by a variable name and a value.
+Defined with `let`, followed by a variable name and a value.
 
 ```thp
-val surname = "Doe"
-val year_of_birth = 1984
+let surname = "Doe"
+let year_of_birth = 1984
 ```
 
 ### Datatype annotation
 
-Same as mutable variables
+Written after the `let` keyword but before the variable name.
 
 ```thp
-val String surname = "Doe"
-val Int year_of_birth = 1984
+let String surname = "Doe"
+let Int year_of_birth = 1984
 ```
 
-When annotating an immutable variable the `val` keyword is optional
+When annotating an immutable variable the `let` keyword is optional
 
 ```thp
 // Equivalent to the previous code
@@ -53,4 +32,32 @@ This means that if a variable has only a datatype, it is immutable.
 
 
 
+## Mutable variables
+
+Defined with `let mut`, followed by a variable name and a value.
+
+```thp
+let mut name = "John"
+let mut age = 32
+```
+
+### Datatype annotation
+
+Written after the `let mut` keywords but before the variable name.
+
+```thp
+let mut String name = "John"
+let mut Int age = 32
+```
+
+When annotating a mutable variable the keyword `let` is optional. `mut` is still **required**.
+
+```thp
+// Equivalent to the previous code
+mut String name = "John"
+mut Int age = 32
+```
+
+
+
 
diff --git a/md/learn/classes/definition.md b/md/learn/classes/definition.md
index 215dbb3..24ea16b 100644
--- a/md/learn/classes/definition.md
+++ b/md/learn/classes/definition.md
@@ -8,7 +8,7 @@ Basically kotlin syntax.
 `new` not required, in fact, forbidden.
 
 ```thp
-val dog = Dog()
+let dog = Dog()
 ```
 
 ## Simple class
@@ -18,7 +18,7 @@ Why'd you do this tho?
 ```thp
 class SimpleClass
 
-val instance = SimpleClass()
+let instance = SimpleClass()
 ```
 
 ## Properties & methods
@@ -27,15 +27,15 @@ val instance = SimpleClass()
 class SimpleClass
 {
     // Properties are private by default
-    var String? name = ...
+    mut String? name = ...
 
     // Made public with `pub`
-    pub var String? surname = ...
+    pub mut String? surname = ...
 
     // Methods are private by default
     fun display_name()
     {
-        // `$` is used instead of $this
+        // `$` is used instead of $this. Mandatory
         print($name)
     }
 
@@ -57,12 +57,30 @@ Kotlin style
 
 
 ```thp
-class Cat(val String name)
+class Cat(
+    // If a parameter has pub, protected or private they are promoted to properties
+    private String name,
+    pub mut Int lives = 9,
+    protected String surname = "Doe",
+)
 {
     pub fun get_name() -> String
     {
         $name
     }
+
+    pub fun die()
+    {
+        $lives -= 1
+        if $lives <= 0
+        {
+            print("Cat {$name} is death")
+        }
+        else
+        {
+            print("Cat {$name} is life still")
+        }
+    }
 }
 
 val michifu = Cat("Michifu")
@@ -72,9 +90,9 @@ print(michifu.get_name())
 With kotlin's `init` block.
 
 ```thp
-class Dog(val String name)
+class Dog(pub String name)
 {
-    val Int name_length
+    Int name_length
 
     init
     {
@@ -89,7 +107,7 @@ class Dog(val String name)
 Kotlin style
 
 ```thp
-class Animal(val String name)
+class Animal(pub String name)
 {
     pub fun say_name()
     {
diff --git a/md/learn/classes/magic.md b/md/learn/classes/magic.md
index cea5970..cc0b331 100644
--- a/md/learn/classes/magic.md
+++ b/md/learn/classes/magic.md
@@ -16,10 +16,10 @@ class Cat
 
 
 ```thp
-val option = Some("GAAA")
-val Some(value) = option
+let option = Some("GAAA")
+let Some(value) = option
 
-val colors = Array("red", "green", "blue")
-val Array()
+let colors = Array("red", "green", "blue")
+let Array()
 
 ```
diff --git a/md/learn/collections/arrays.md b/md/learn/collections/arrays.md
index ccfeb6a..a91c975 100644
--- a/md/learn/collections/arrays.md
+++ b/md/learn/collections/arrays.md
@@ -6,13 +6,13 @@ for constructing arrays
 ## Usage
 
 ```thp
-val fruits = Array("apple", "banana", "cherry")
-val apple = fruits.[0]
+let fruits = Array("apple", "banana", "cherry")
+let apple = fruits.[0]
 
 print(apple)
 
 
-var numbers = Array(0, 1, 2, 3)
+let mut numbers = Array(0, 1, 2, 3)
 
 // Note the dot
 numbers.[3] = 5
diff --git a/md/learn/collections/maps.md b/md/learn/collections/maps.md
index b6d5e3a..fd3f81f 100644
--- a/md/learn/collections/maps.md
+++ b/md/learn/collections/maps.md
@@ -6,7 +6,7 @@ Also known as Associative Arrays
 ## Usage without a declaration
 
 ```thp
-var person = Obj {
+let mut person = Obj {
     name: "John",
     surname: "Doe",
     age: 33,
@@ -31,7 +31,7 @@ obj Person = {
 }
 
 
-val john_doe = Person {
+let john_doe = Person {
     name: "John",
     surname: "Doe",
     age: 33,
diff --git a/md/learn/collections/sets.md b/md/learn/collections/sets.md
index 357823a..75932f1 100644
--- a/md/learn/collections/sets.md
+++ b/md/learn/collections/sets.md
@@ -3,7 +3,7 @@
 
 ```thp
 // Set[Int]
-val ages = Set(30, 31, 33, 35)
+let ages = Set(30, 31, 33, 35)
 
 for age in ages {
     print("{age}")
diff --git a/md/learn/collections/tuples.md b/md/learn/collections/tuples.md
index 3db7b71..cd53916 100644
--- a/md/learn/collections/tuples.md
+++ b/md/learn/collections/tuples.md
@@ -6,9 +6,9 @@ calls (`()`).
 ## Definition
 
 ```thp
-val person = #("John", "Doe", 32)
+let person = #("John", "Doe", 32)
 
-val #(name, surname, age) = person
+let #(name, surname, age) = person
 ```
 
 
diff --git a/md/learn/flow-control/conditionals.md b/md/learn/flow-control/conditionals.md
index 0846b95..9a69c41 100644
--- a/md/learn/flow-control/conditionals.md
+++ b/md/learn/flow-control/conditionals.md
@@ -22,7 +22,7 @@ else
 }
 
 
-val result = if condition { value1 } else { value2 }
+let result = if condition { value1 } else { value2 }
 ```
 
 
@@ -40,7 +40,7 @@ if variable is Datatype
 ## If variable is of enum
 
 ```thp
-val user_id = POST::get("user_id")
+let user_id = POST::get("user_id")
 
 if Some(user_id) = user_id
 {
diff --git a/md/learn/flow-control/loops.md b/md/learn/flow-control/loops.md
index 65ce386..96c7c64 100644
--- a/md/learn/flow-control/loops.md
+++ b/md/learn/flow-control/loops.md
@@ -5,7 +5,7 @@
 Braces are required.
 
 ```thp
-val numbers = Array(0, 1, 2, 3)
+let numbers = Array(0, 1, 2, 3)
 
 for number in numbers
 {
@@ -19,7 +19,7 @@ for #(index, number) in numbers.entries()
 ```
 
 ```thp
-val dict = Obj {
+let dict = Obj {
     "apple": 10,
     "banana": 7,
     "cherries": 3,
@@ -45,8 +45,8 @@ for value in collection
 ## While loop
 
 ```thp
-val colors = Array("red", "green", "blue")
-var index = 0
+let colors = Array("red", "green", "blue")
+let mut index = 0
 
 while index < colors.size()
 {
diff --git a/md/learn/flow-control/match.md b/md/learn/flow-control/match.md
index ed2dc14..a5858b3 100644
--- a/md/learn/flow-control/match.md
+++ b/md/learn/flow-control/match.md
@@ -1,13 +1,15 @@
 # Match
 
-## Most likely syntax
+## Syntax
+
+Braces are **required**.
 
 ```thp
-val user_id = POST::get("user_id")
+let user_id = POST::get("user_id")
 
 
 match user_id
-| Some(id){ print("user_id exists: {id}") }
+| Some(id) { print("user_id exists: {id}") }
 | None { print("user_id doesn't exist") }
 
 match user_id
@@ -34,23 +36,4 @@ match user_id
 
 ```
 
-## Alternative syntax?
-
-```thp
-// Alternative syntax?
-
-match user_id {
-    Some(id) { print("user_id exists: {id}") }
-    None { print("user_id doesn't exist") }
-}
-
-match user_id {
-    Some(id) {
-        print("user_id exists: {id}")
-    }
-    None {
-        print("user_id doesn't exist")
-    }
-}
-```
 
diff --git a/md/learn/functions/declaration.md b/md/learn/functions/declaration.md
index b14935a..43c0a06 100644
--- a/md/learn/functions/declaration.md
+++ b/md/learn/functions/declaration.md
@@ -21,7 +21,7 @@ fun get_random_number() -> Int
     Random::get(0, 35_222)
 }
 
-val number = get_random_number()
+let number = get_random_number()
 ```
 
 ## With parameters and return type
@@ -32,7 +32,7 @@ fun get_secure_random_number(Int min, Int max) -> Int
     Random::get_secure(min, max)
 }
 
-val number = get_secure_random_number(0, 65535)
+let number = get_secure_random_number(0, 65535)
 ```
 
 
@@ -44,10 +44,10 @@ fun get_first_item[T](Array[T] array) -> T
     array.[0]
 }
 
-val first = get_first_item[Int](numbers)
+let first = get_first_item[Int](numbers)
 // The type annotation is optional if the compiler can infer the type
 
-val first = get_first_item(numbers)
+let first = get_first_item(numbers)
 ```
 
 
diff --git a/md/learn/functions/higher-order.md b/md/learn/functions/higher-order.md
index 4ae4bd4..2bc3040 100644
--- a/md/learn/functions/higher-order.md
+++ b/md/learn/functions/higher-order.md
@@ -23,8 +23,8 @@ fun generate_generator() -> () -> Int
 }
 
 
-val generator = generate_generator()  // A function
-val value = generate_generator()()    // An Int
+let generator = generate_generator()  // A function
+let value = generate_generator()()    // An Int
 ```
 
 
diff --git a/md/learn/functions/lambdas.md b/md/learn/functions/lambdas.md
index 02e1bb8..36c22de 100644
--- a/md/learn/functions/lambdas.md
+++ b/md/learn/functions/lambdas.md
@@ -22,7 +22,7 @@ By default closures **always** capture variables as **references**.
 
 
 ```thp
-var x = 20
+let mut x = 20
 
 val f = fun() {
     print(x)
@@ -44,7 +44,7 @@ fun(parameters) clone(variables) {
 ```
 
 ```thp
-var x = 20
+let mut x = 20
 
 val f = fun() clone(x) {
     print(x)
diff --git a/md/learn/functions/parameters.md b/md/learn/functions/parameters.md
index 62e0e31..9e77b76 100644
--- a/md/learn/functions/parameters.md
+++ b/md/learn/functions/parameters.md
@@ -14,7 +14,7 @@ properties can be used inside the function
 
 ```thp
 fun count(Array[Int] numbers) -> Int {
-    val items_count = numbers.size()    // Ok, `size` is pure
+    let items_count = numbers.size()    // Ok, `size` is pure
 
     items_count
 }
@@ -36,7 +36,7 @@ data **can** be mutated.
 The caller *must* also use `&`.
 
 ```thp
-val numbers = Array(0, 1, 2, 3)
+let numbers = Array(0, 1, 2, 3)
 
 push_25(&numbers)    // Pass `numbers` as reference.
 
@@ -58,7 +58,7 @@ of the parameter (CoW). The original data will **not** be mutated.
 
 
 ```thp
-val numbers = Array(1, 2, 3, 4)
+let numbers = Array(1, 2, 3, 4)
 
 add_25(numbers)    // Pass `numbers` as clone.
 
diff --git a/md/learn/ideas/idea_1.md b/md/learn/ideas/idea_1.md
index 7d8d54d..dab5b65 100644
--- a/md/learn/ideas/idea_1.md
+++ b/md/learn/ideas/idea_1.md
@@ -1,8 +1,8 @@
 # Idea 1
 
 
-var x = 20
-val y = 30
+let mut x = 20
+let y = 30
 
 type Something = ...
 
@@ -21,8 +21,8 @@ fun do_something(&Something some) -> Bool {}
 do_something(&s1)
 
 
-var arr1 = Array(10, 20, 30)
-var arr2 = &arr1
+let mut arr1 = Array(10, 20, 30)
+let mut arr2 = &arr1
 
 
             Owned/Reference     Mutable
@@ -51,9 +51,9 @@ returns those new values in a new array.
 ### Example
 
 ```thp
-val numbers = Array(1, 2, 3, 4, 5)
+let numbers = Array(1, 2, 3, 4, 5)
 
-val numbers_squared = numbers.map {it ** 2}
+let numbers_squared = numbers.map {it ** 2}
 
 print(numbers_squared)  // Array(1, 4, 9, 16, 25)
 
@@ -80,22 +80,22 @@ Iteratively reduce the array to a single value using `callback`.
 ### Example
 
 ```thp
-val numbers = Array(1, 2, 3, 4, 5)
+let numbers = Array(1, 2, 3, 4, 5)
 
-val sum = numbers.reduce(0, \+)
-val sum = numbers.reduce(0) {$1 + $2}
-val sum = numbers.reduce(0, fun(prev, curr) {prev + curr})
+let sum = numbers.reduce(0, \+)
+let sum = numbers.reduce(0) {$1 + $2}
+let sum = numbers.reduce(0, fun(prev, curr) {prev + curr})
 
 print(sum)  // 15
 ```
 
 
 ```thp
-val numbers = Array(1, 2, 3, 4, 5)
+let numbers = Array(1, 2, 3, 4, 5)
 
-val sum = numbers.reduce("", fun(prev, curr) {prev + curr})
+let sum = numbers.reduce("", fun(prev, curr) {prev + curr})
 
-val sum = numbers.reduce("") {prev, curr -> prev + curr}
+let sum = numbers.reduce("") {prev, curr -> prev + curr}
 
 print(sum)  // "12345"
 ```
@@ -145,7 +145,7 @@ fun (>>=)[m, A, B](
 
 (Array[Int], Int -> Array[String]) -> Array[String]
 
-val result = Array(1, 2, 3, 4, 5) >>= {Array($.into[String]())}
+let result = Array(1, 2, 3, 4, 5) >>= {Array($.into[String]())}
 
 print(result)   // Array("1", "2", "3", "4", "5")
 ```
@@ -194,7 +194,7 @@ fun (>>)[A, B, C](
     (B) -> C,
 ) -> (A) -> C
 
-val f1 = add1 >> times2
+let f1 = add1 >> times2
 
 f1(5)   // 12
 ```
diff --git a/md/learn/index.md b/md/learn/index.md
index e9cbb5c..5ce436a 100644
--- a/md/learn/index.md
+++ b/md/learn/index.md
@@ -25,7 +25,7 @@ If you want to learn the language, go to the learn section.
 - Create a **consistent** language.
 - Create typings for popular libraries (like TS's `.d.ts`).
 - Have a simple instalation and configuration (requiring just Composer).
-- Ship a fast, native binary (not written in PHP).
+- Ship a fast, native binary (written in Rust) (why use PHP when we can go native?).
 - Sub 10ms watch mode.
 - Support in-place compilation.
 - Emit readable PHP code.
@@ -47,16 +47,154 @@ These are **not** aspects that THP looks to solve or implement.
 - Change over conventions
 - Explicit over implicit
 
-That is, while there is value in the items on
-the right, we value the items on the left more.
 
-## Compared to PHP
+## Some differences with PHP
 
-### Differences
+```thp
+// PHP
+$has_key = str_contains($haystack, 'needle');
 
-### Runtime similarities
+// THP
+val has_key = haystack.contains("needle")
+```
 
-## Improvements
+- Explicit variable declaration
+- No `$` for variable names (and thus no `$$variable`)
+- No semicolons
+- Use methods on common datatypes
+- Strings use only double quotes
+
+---
+
+```thp
+// PHP
+[
+    'names' => ['Toni', 'Stark'],
+    'age' => 33,
+    'numbers' => [32, 64, 128]
+]
+
+// THP
+Obj {
+    names: #("Toni", "Stark"), // Tuple
+    age: 33,
+    numbers: [32, 64, 128]
+}
+```
+
+- Tuples, Arrays, Sets, Maps are clearly different
+- JS-like object syntax
+
+---
+
+```thp
+// PHP
+$cat = new Cat("Michifu", 7);
+$cat->meow();
+
+// THP
+val cat = Cat("Michifu", 7)
+cat.meow();
+```
+
+- No `new` for classes
+- Use dot `.` instead of arrow `->` syntax
+
+---
+
+
+```thp
+// PHP
+use \Some\Deeply\Nested\Class
+use \Some\Deeply\Nested\Interface
+
+// THP
+use Some::Deeply::Nested::{Class, Interface}
+```
+
+- Different module syntax
+- PSR-4 required
+- No `include` or `require`
+
+---
+
+Other things:
+
+- Pattern matching
+- ADTs
+
+
+### Runtime changes
+
+THP should add as little runtime as possible.
+
+```thp
+// ===== current =======
+val name = "John"
+var name = "John"
+
+String name = "John"
+var String name = "John"
+
+
+
+// ===== new? =======
+let name = "John"
+let mut name = "John"
+
+String name = "John"
+mut String name = "John"
+
+
+// For primitive datatypes (Int, Float, Bool, String?)
+
+// Cloned
+fun add(Int x)
+// Still cloned, but the x **binding** can be mutated, not the original variable
+fun add(mut Int x)
+// Same as 1st
+fun add(clone Int x)
+
+
+// For other datatypes
+
+// Pass an immutable reference
+fun add(Obj o)
+// Pass a mutable reference
+fun add(mut Obj o)
+// Clone the argument
+fun add(clone Obj o)
+
+
+// Only references are passed, not "variables" (as PHP calls them)
+let john = Obj {name: "John"}
+/*
+    john --------> {name: "John"}
+*/
+
+fun set_empty(mut Obj person) {
+    /*
+        john ------┬-->  {name: "John"}
+        person ----┘ 
+    */
+
+    // This creates a **new** Obj, and the variable `person` now points to it.
+    person = Obj {name: "Alex"}
+    /*
+        john --------->  {name: "John"}
+        person ------->  {name: "Alex"}
+    */
+}
+
+set_empty(mut obj)
+
+print(obj)  // Obj {name: "John"}
+
+```
+
+
+
+## Example
 
 ```thp
 use PDO
diff --git a/static/js/prism.thp.js b/static/js/prism.thp.js
index 2805980..bbf6baa 100644
--- a/static/js/prism.thp.js
+++ b/static/js/prism.thp.js
@@ -15,7 +15,7 @@ Prism.languages.thp = {
         pattern: /(["])(?:\\(?:\r\n|[\s\S])|(?!\1)[^\\\r\n])*\1/,
         greedy: true,
     },
-    "keyword": /\b(?:static|const|enum|loop|use|break|catch|continue|do|else|finally|for|fun|if|in|fn|nil|return|throw|try|while|val|var|type|match|with|of|abstract|class|interface|private|pub|obj|override|open|init)\b/,
+    "keyword": /\b(?:static|const|enum|loop|use|break|catch|continue|do|else|finally|for|fun|if|in|fn|nil|return|throw|try|while|type|match|with|of|abstract|class|interface|private|pub|obj|override|open|init|let|mut)\b/,
     "number": /\b0x[\da-f]+\b|(?:\b\d+(?:\.\d*)?|\B\.\d+)(?:e[+-]?\d+)?/i,
     "operator": /[<>]=?|[!=]=?=?|--?|\$|\+\+?|&&?|\|\|?|[?*/~^%]/,
     "punctuation": /[{}[\];(),.]/,