Try adding one or more LEDs to your project. Adjust your code so the new LEDs behave exactly like the original five.
Now, change your sketch so the LEDs turn on in order from pin 2 to 6, but turn off in reverse—from pin 6 back to 2.
Want a challenge? Make every second LED blink twice, slow the sequence down gradually, or reverse the entire direction based on a variable. Be creative!
After each change, upload the sketch and test it on your board. Debug as needed and enjoy experimenting.