'''
Mission 11 - Spirit Level
The program uses the accelerometer to determine if CodeX
is level, using only the x (vertical) measurement. 
Concepts learned: 
    reading from the accelerometer, using one value
    from the tuple, filling the display in a different
    color, drawing lines and drawing circles
'''

from codex import *
from time import sleep
import math
# center of display (240 x 240)
CENTER = 120

# draw two lines on the screen
# leave space in the middle for the circle 
display.fill(WHITE)
display.draw_line(CENTER, 0, CENTER, 105, BLACK)
display.draw_line(CENTER, 135, CENTER, 239, BLACK)

# define a variable to use for the circle's position
x = CENTER

# start an infinite loop
while True:
    # read from the accelerometer and get x value
    val = accel.read()
    tilt_x = val[0]
    # change accelerometer reading to degrees
    scaled = (tilt_x / 16384)
    scaled = min(max(scaled, -1), 1)
    degrees = math.asin(scaled) * 180 / math.pi
    degrees = int(degrees)
    # erase current circle, recalculate, and draw new circle
    display.draw_circle(x, CENTER, 15, WHITE)
    x = CENTER + degrees
    display.draw_circle(x, CENTER, 15, ORANGE)
    sleep(0.5)