diff --git a/2021/day12.js b/2021/day12.js
new file mode 100644
index 0000000..48ef7d2
--- /dev/null
+++ b/2021/day12.js
@@ -0,0 +1 @@
+s='start',e='end',M={},b=(f,t)=>{if(f!=e&&t!=s)M[f]=[...(M[f]||[]),t]};$`pre`.innerText.split`\n`.map(l=>{[f,t]=l.split`-`;b(f,t);b(t,f)});C=(h,d)=>(L=h[h.length-1],L==e?1:(L>']'&&h.slice(0,-1).includes(L)&&d++)?0:M[L].reduce((a,t)=>a+C([...h,t],d),0));[1,0].map(x=>C([s],x))
\ No newline at end of file