1. `file` it

┌──(kali㉿kali)-[~/code]
└─$ file flag.txt
flag.txt: PNG image data, 1697 x 608, 8-bit/color RGB, non-interlaced
                                

2. how about `strings`?

┌──(kali㉿kali)-[~/code]
└─$ strings flag.txt | grep "pico"
                                      

...still not working
3. change the file name from `.txt` to `png`
TADA!