# Code Ninja Tutorial - Variables and Mathematics

Variables in Code Ninja are containers that store values. They can hold numbers and are extremely useful in making your code more flexible and reusable.

## Setting and Using Variables

### Creating a Variable

• To create a variable, use the `var` command followed by a name and a value.
• Example: `var length 100` creates a variable named `length` with a value of 100.

### Using Variables in Commands

• Use a dollar sign `\$` before the variable name to use its value.
• Example: `fd \$length` moves the pointer forward by the value stored in `length`.

## Basic Mathematical Operations

Code Ninja supports basic math operations, enabling you to alter variable values.

### Math Commands

• `add`, `sub`, `mul`, `div`: Perform addition, subtraction, multiplication, and division.
• Example: `var length add \$length 50` increases `length` by 50. Think of this as ‘length = length + 50’.

### Using Math in Drawing

• Alter the value of variables to change the dimensions of shapes dynamically.
• Example: Increase the length each time you draw a side.

## Exercise: Drawing a Polygon Using Variables and Math

Let’s put variables and math to use by drawing a polygon. We’ll make each side longer than the previous one.

``````// Set up the variables
var length 30
var angle 50

// Draw the pattern.
repeat 30 {
fd \$length
rt \$angle
var length add \$length 5
}
``````