Hide the Needle in the Haystack (Cops)
Haystack, 84 bytes, Cracked

0\\1-c\
//    
?10F17+c8F+4+cd8F+3+c6-c1+c,c2+c8+c|
 0   \1++c,c|
F/c++2F8
c\8F+2+cd


Try it online!

This looks (to me) rather convoluted but if you find the right subset it's a bit too easy... oh well, just to get us started :P