2ヶ月くらい前にサーバにイースターエッグ仕込んだ時に書いたのを見つけた。
<!DOCTYPE html><html><head><style>pre{font-family:"menlo","courier",monospace;}</style></head><body><pre id="map"> ------ --------- |....| ####........| |.....### |.......| --.--- |.......| # ---.----- ############## </pre><br /><pre>h - left\nj - down\nk - up\nl - right</pre><script> var map=document.querySelector('#map'),w=21,h=6,idx,cell,mt,okc=['.','#'],ok;ok=function(c){return okc.indexOf(c)>-1;};omt=mt=map.textContent;map.textContent=omt.replace(/\./,"@");document.addEventListener('keypress',function(e){mt=map.textContent;idx=mt.indexOf('@');switch(e.keyCode){case 104:if(ok(mt[idx-1]))map.textContent=omt.slice(0,idx-1)+"@"+omt.slice(idx);break;case 108:if(ok(mt[idx+1]))map.textContent=omt.slice(0,idx+1)+"@"+omt.slice(idx+2);break;case 107:if(ok(mt[idx-w-1]))map.textContent=omt.slice(0,idx-w-1)+"@"+omt.slice(idx-w);break;case 106:if(ok(mt[idx+w+1]))map.textContent=omt.slice(0,idx+w+1)+"@"+omt.slice(idx+w+2);break;}}); </script></body></html>