'''
Mission 7 - Personal Billboard
Medium Remix 2D
This project creates a list with math facts. In order to 
print on multiple lines, display.print() must be used.
However, it scrolls continuously, so the code for displaying
was moved inside each button press to stop the scrolling.
This isn't the only way to do it, but an option of students
get frustrted. 
- It includes a button to break the loop and quit -
'''
from codex import *
from time import sleep

choice = 0
my_list = ["Area of square: \n side x side", 
            "Area of rectangle: \n length x width",
            "Area of circle: \n pi x radius x radius", 
            "Area of right triangle: \n length x width / 2",
            "Perimeter of square: \n side x 4",
            "Perimeter of rect: \n length x 2 + width x 2",
            "Circumference: \n 2 x pi x radius",
            "Perim of triangle: \n side1 + side2 + side3"]
LAST_INDEX = len(my_list) - 1

# MAIN PROGRAM
while True:
    # display instructions 
    display.clear()
    display.show("Press L/R to scroll")
    sleep(1)
    display.clear()

    # scroll backward and display item
    if buttons.was_pressed(BTN_L):
        choice = choice - 1
        if choice < 0:
            choice = LAST_INDEX
        my_image = my_list[choice]
        display.print(my_image)
        sleep(2)
        
    # scroll forward and display item
    if buttons.was_pressed(BTN_R):
        choice = choice + 1
        if choice > LAST_INDEX:
            choice = 0
        my_image = my_list[choice]
        display.print(my_image)
        sleep(2)
   
    # break out of loop and quit
    if buttons.was_pressed(BTN_D):
        break