World's Hardest 15-Puzzle

This is a surprinsing version of the 15-puzzle game I found in my great-great-great-grandfather's trunk. Whereas the original 140 years old game has its 15 pieces numbered from 1 to 15 (hence its name), this one has no numbers, all pieces are the same. At first I wondered what kind of joke this was, with its boasting "World's Hardest 15-puzzle"? All pieces are identical, game's resolved! That is, until I began fiddling with it and saw some pieces lighting on! Then I figured each piece has its intended place where it lights up, and the game's done once all pieces shine.

I also found a vintage printed ad about this game which confirms this. It looks like the game was a novelty trinket from the Wild West era, and from what I've been told about my ancestor that would quite fit his adventurous personnality. But, this is still bewildering. I never heard of this, had it any success? Is there any other copy of this? How does it work? How come it still works after more than a century? It seems this was manufactured in France, I wonder whether I can find any more information here.

Anyway, here's a rough copy of that ad, I hope I'll find some time to scan it:

You already know the 15 puzzle which recently became a widespread phenomon. A mere toy for children, may you think? Yet let us show you how demanding that game can be with this amazing brain twister coming straight from France! Imagine:
- All pieces are strictly identical, with no distinguishable detail.
- Where the hole should be changes with every game.
- Each block lights on only once in place, thanks to the magic of electricity!

Only possible thanks to modern science!
Train your brain, improve your hand & eye coordination!
Each play is a new game!
Totally safe!
High durability!
Play it everywhere!
Made with the most delicate materials from France!
It'll cost you only what you want!

Controls

• Arrow keys or gamepad to switch hole with a piece next to it.
• To start another game press Enter and select "Reset cart".

The game was made for the Thinky Puzzle Game Jam and in 560 chars or less for the Tweet Tweet Jam 6. If you have Pico-8 you can copy & paste the code below to play the exact same game on it.

function m(b)
s=u+({1,-1,4,-4})[b+1]
if((b<2and u\4==s\4)or(b>1and s>=0and s<16))t[s+1],t[u+1]=t[u+1],t[s+1]u=s
end
i="\^y9world's hardest\n\^t\^w\-a15-puzzle"t={}h=rnd(16)\1u=h
for n=0,15 do
add(t,n)end
for n=0,999do m(rnd(4)\1)end::_::cls(4)
?i,34,14,2
?i,35,13,9
for n=-1,#t-1 do
l=-2x=30y=38w=66k=0d=2j=0c=circ
if(n>-1)x=n%4*16+32y=(n-n%4)*4+40l=t[n+1]w=14k=2j=4d=1
if(l==n)k=9j=10d=4c=circfill
if(l==h)w=12k=1j=1d=1y+=2
rectfill(x,y,x+w,y+w,k)
for o=0,3do pset(x+o%2*w,y+o\2*w,d)end c(x+7,y+7,3,j)
end
for b=0,3 do
if(btnp(b))m(b)
end
flip()goto _