Other students:
#define redLed 2
#define yellowLed 3
#define greenLed 4
void setup ()
{
pinMode(redLed, OUTPUT);
pinMode(yellowLed, OUTPUT) ;
pinMode(greenLed, OUTPUT) ;
}
Me:
void setup ()
{
for (int i=2;i<5;i++)
pinMode (i, OUTPUT);
}
Proff - This code is wrong it won't work. Where have you specified red led, green led, yellow led?
Me - wtf! Code doesn't know which led is used in what pin it's just pin numbers!

Gave me less marks 😑
P. S. I wrote comments in my code specifying which pin will have what led connected 😑