function calcBF(){var kicks=parseInt(document.getElementById("kicks").value)||8;var level=document.getElementById("level").value;var rating=kicks<6?"Too few — add more kicks":kicks>10&&level!="advanced"?"Consider reducing to 6-8":level==="advanced"&&kicks>=8?"Good power":"Efficient pattern";document.getElementById("r1").textContent=rating;document.getElementById("r2").textContent=kicks+" kicks/25m";document.getElementById("desc").innerHTML="Your butterfly: "+kicks+" dolphin kicks per 25m
"+rating+"
Butterfly tip: the second kick (after the pull) should be the most powerful. Practice 2-kick-1-pull and 1-kick-1-pull patterns.";document.getElementById("results").style.display="block";}