introduction done

Introduction/chapter1.md

@@ -306,6 +306,16 @@ Start with a brute force solution, compare it with BCR, find a middle-point algo
 
 If you've reached BCR and have O(1) additional space, you can't optimize big O time or space.
 
+### 1.2.3. What good coding looks like
+
+* correct
+* efficient, time and space
+* simple/short
+* readable, comments when necessary
+* maintainable, using classes for example
+* modular, separate isolated chunks of code into their own methods
+* flexible and robus, generalize for NxN instead of 3x3 in tic-tac-toe.
+* error checking, don't assume input data type. validate the input with 'assert' or if statements
 
 ## General resources