Click on box
		- if is a text box, move the cursor inside the text;
		- if is not a text box (operators), select that box;

	 Drag and drop
		- drag and drop all formula;

	← LEFT KEY
		- if you are in a text box in the midle of text, moves the cursor on the left char;
		- if you are in a text box at left, moves the cursor in the next left box if exist;
		- if the current node is a box, moves the cursor on the next left box;
	→ RIGHT KEY
		- if you are in a text box in the midle of text, moves the cursor on the right char;
		- if you are in a text box at right, moves the cursor in the next right box if exist;
		- if the current node is a box, moves the cursor on the next right box;
	↑ UP KEY
		- select the parent node of the current node;
	↓ DOWN KEY
		- select first child node of the current node;
	 TAB KEY
		- if you are in a text box, moves the cursor from text to text, from left to right;
		- if you are in a box, moves the cursor from box to box, from left to right;
	 SHIFT + TAB KEY
		- if you are in a text box, moves the cursor from text to text, from right to left;
		- if you are in a box, moves the cursor from box to box, from right to left;
	 DELETE KEY
		- if you are in a text box, delete the char from right;
		- if you are in a box, delete that box and select next right node;
	 BACKSPACE KEY
		- if you are in a text box, delete the char from left;
		- if you are in a box, delete that box and select next left node;
	 ENTER KEY
		- if you are in a text box, creates a new node (...) to the right of this text block;
		- if you are in a box, delete that box and replace with a new node (...);

	 Add / change paranthesis to a box
		- select that box and click on of paranthesis button;