Python - moviepy - animated text

from moviepy.editor import *

# --- functions ---

def move(x1, y1, x2, y2, time):
    step_x = (x2 - x1) / time
    step_y = (y2 - y1) / time
    return lambda t: (x1 + t*step_x, y1 + t*step_y)

# --- main ---

video_size = (600,600)

# ---

text_clip_1 = TextClip('Hello', color='red', font='Amiri-Bold', kerning=5, fontsize=60)

txt_width = text_clip_1.size[0]
txt_height = text_clip_1.size[1]

y = (600-txt_height)//2
right_x = 600-txt_width
time = 1.5

move_right = text_clip_1.set_position(move(0, y, right_x, y, time), 0).set_duration(time)
move_left  = text_clip_1.set_position(move(right_x, y, 0, y, time), 0).set_duration(time).set_start(time)

# ---

text_clip_2 = TextClip('World', color='red', font='Amiri-Bold', kerning=5, fontsize=60)

txt_width = text_clip_2.size[0]
txt_height = text_clip_2.size[1]

x = (600-txt_width)//2
bottom_y = 600-txt_height
time = 1.5

move_down = text_clip_2.set_position(move(x, 0, x, bottom_y, time), 0).set_duration(time)
move_up   = text_clip_2.set_position(move(x, bottom_y, x, 0, time), 0).set_duration(time).set_start(time)

# ---

output_clip = CompositeVideoClip([
    move_right, move_left,
    move_down, move_up
], video_size)

output_clip.fps = 24
output_clip.write_videofile('animation.avi', fps=24, codec='mpeg4')#, ffmpeg_params=['-s', '600x600'])

# ffmpeg -i animation.avi -s 300x300 animation.gif