Rating: 4.0

# DDR

First thing that came to mind looking at this picture was that I could follow some path starting from the center arrow, and then use 0 or 1 from the tiles background, which would encode a message. Unfortunaly, I quickly noticed there are some loops in, and therefore took a step back.

I then looked closer: each tile actually has a different grayscale level. Maybe they encode different things? I suspected that we should start still from the red tile, so i checked the next few tiles in the sequence. Got it! They have grayscale values of 0x61, 0x6C, 0x67, 0x7B, which reads "lag{" in ASCII! Therefore the red tile is the "f", and we can read "flag{" to start with.

I took a risk and assumed that if I run the path from here automatically, surely the flag will appear (otherwise, well, F, i can try something different). Next step was to automate things quickly. I took the RGB values of each arrow at position (6, 32) in the tile because that's the position where, for any arrow type, we still hit a unique color identifying the arrow. Then I just use the directions to traverse and read the grayscale code of the tile and convert it to char. Loop until we hit an "}" character!


from PIL import Image

# parse direction from colors
def getDirection(colorCode):
r, g, b, _ = colorCode
if(b > g and b > r and r > g):
return "up"
if(r > g and r > b):
return "down"
if(r < g and b < g):
return "left"
if(b > g and b > r and r < g):
return "right"
return "ERROR"

# pixel that always hits the arrow color
def getColorCode(pix, x, y):
return pix[6+64*x, 32+64*y]

# decode bit to get ascii later
def getBit(pix, x, y):
r, _, _, _ = pix[1+64*x, 1+64*y]
return r

im = Image.open('ddr.png')
print(im.size)

# start from one step ahead (skip the red square, it's "f")
x = 11
y = 7
curr = 0
flag = "f"

# until you finish the flag
while chr(curr) != '}':
curr = getBit(pix, x, y)
flag += chr(curr)
dir = getDirection(getColorCode(pix, x, y))
if dir == "down":
y += 1
if dir == "up":
y -= 1
if dir == "left":
x -= 1
if dir == "right":
x += 1
x = x % 21
y = y % 15
print(flag)

# BINGO
print(f"\nfound it! {flag}")



We get a very sweet output as the path is taken!


(1344, 960)
fl
fla
flag
flag{
flag{2
flag{2a
flag{2a4
flag{2a4c
flag{2a4c6
flag{2a4c67
flag{2a4c670
flag{2a4c6706
flag{2a4c67067
flag{2a4c670674
flag{2a4c6706740
flag{2a4c67067402
flag{2a4c670674023
flag{2a4c670674023b
flag{2a4c670674023b9
flag{2a4c670674023b97
flag{2a4c670674023b972
flag{2a4c670674023b972f
flag{2a4c670674023b972f4
flag{2a4c670674023b972f4e
flag{2a4c670674023b972f4ef
flag{2a4c670674023b972f4ef2
flag{2a4c670674023b972f4ef2b
flag{2a4c670674023b972f4ef2bc
flag{2a4c670674023b972f4ef2bc1
flag{2a4c670674023b972f4ef2bc19
flag{2a4c670674023b972f4ef2bc192
flag{2a4c670674023b972f4ef2bc1922
flag{2a4c670674023b972f4ef2bc19224
flag{2a4c670674023b972f4ef2bc19224e
flag{2a4c670674023b972f4ef2bc19224e2
flag{2a4c670674023b972f4ef2bc19224e25
flag{2a4c670674023b972f4ef2bc19224e25}

found it! flag{2a4c670674023b972f4ef2bc19224e25}


Overall, I was gonna be fooled by the 0 and 1 thing. Lucky enough I didn't think about the Dance Dance Revolution game and just went straight on following the arrows and decoding something as I'm doing so!