*{margin:0;padding:0;box-sizing:border-box}
:root{--bg:#0a0b0f;--bg2:#11131a;--card:#161922;--card2:#1a1e28;--border:#232733;--border2:#2d3340;--text:#e8eaf0;--dim:#7a8190;--accent:#4f8cff;--hover:#6ba1ff;--green:#2ecc71;--red:#ff3b3b;--gold:#fdcb6e;--r:16px}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;background:var(--bg);color:var(--text);min-height:100vh;line-height:1.7;overflow-x:hidden}
.navbar{display:flex;justify-content:space-between;align-items:center;padding:.75rem 2rem;border-bottom:1px solid var(--border);position:sticky;top:0;background:rgba(10,11,15,.92);backdrop-filter:blur(12px);z-index:50}
.navbar .brand{font-weight:800;color:var(--text);text-decoration:none;font-size:1.05rem;display:flex;align-items:center;gap:.4rem}
.navbar .nav-links{display:flex;gap:1rem}
.navbar .nav-links a{color:var(--dim);text-decoration:none;font-size:.82rem;transition:color .2s;min-height:44px;display:inline-flex;align-items:center}
.navbar .nav-links a:hover,.navbar .nav-links a.active{color:var(--hover)}
main{max-width:1040px;margin:0 auto;padding:2.5rem 2rem 3rem}
h1{font-size:2.2rem;margin-bottom:.4rem;background:linear-gradient(135deg,#4f8cff,#6ba1ff,#55efc4);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.subtitle{color:var(--dim);font-size:1rem;margin-bottom:2rem}
h2{font-size:1.15rem;margin:1.5rem 0 .6rem;color:var(--hover)}
p{margin-bottom:.75rem}a{color:var(--hover)}
ul{margin:0 0 1rem 1.25rem}li{margin-bottom:.4rem}

/* Mode tabs */
.mode-btns{display:flex;gap:.5rem;flex-wrap:wrap;margin-bottom:1.5rem}
.mode-btn{background:var(--bg2);border:1px solid var(--border2);border-radius:999px;padding:.55rem 1.2rem;font-size:.85rem;color:var(--dim);cursor:pointer;transition:all .15s;font-family:inherit;min-height:44px;display:inline-flex;align-items:center}
.mode-btn:hover{border-color:var(--accent);color:var(--text)}
.mode-btn.active{background:linear-gradient(135deg,var(--accent),#3a78f0);border-color:var(--accent);color:#fff;box-shadow:0 4px 14px rgba(79,140,255,.3)}

/* Calculator card */
.tool-card{background:linear-gradient(180deg,var(--card),var(--card2));border:1px solid var(--border2);border-radius:var(--r);padding:2rem;margin-bottom:1.5rem;box-shadow:0 8px 32px rgba(0,0,0,.3)}
.calc-question{font-size:1.15rem;color:var(--text);margin-bottom:1.5rem;font-weight:500}
.input-line{display:flex;align-items:center;flex-wrap:wrap;gap:.6rem;margin-bottom:1rem}
.input-line .field{display:inline-flex;align-items:center;gap:.4rem}
.input-line input{width:130px;min-width:0;background:var(--bg2);border:1px solid var(--border2);border-radius:10px;padding:.7rem .9rem;color:var(--text);font-size:1.1rem;font-family:inherit;text-align:center;transition:border-color .15s,box-shadow .15s}
.input-line input:hover{border-color:var(--accent)}
.input-line input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px rgba(79,140,255,.15)}
.input-line .unit{color:var(--dim);font-size:1.1rem;font-weight:600}
.input-line .op{color:var(--accent);font-size:1.3rem;font-weight:700;padding:0 .2rem}
.btn-row{display:flex;gap:.6rem;flex-wrap:wrap;margin-top:.5rem}
.btn{background:linear-gradient(135deg,var(--accent),#3a78f0);color:#fff;border:none;border-radius:10px;padding:.75rem 1.8rem;font-size:.9rem;font-weight:600;cursor:pointer;transition:transform .1s,box-shadow .15s;font-family:inherit;min-height:44px;box-shadow:0 4px 14px rgba(79,140,255,.3)}
.btn:hover{box-shadow:0 6px 20px rgba(79,140,255,.45)}
.btn:active{transform:scale(.97)}
.btn-secondary{background:var(--bg2);border:1px solid var(--border2);box-shadow:none}
.btn-secondary:hover{background:var(--card);box-shadow:none}

/* Result */
.result-box{background:linear-gradient(135deg,rgba(46,204,113,.12),rgba(79,140,255,.08));border:1px solid rgba(46,204,113,.3);border-radius:var(--r);padding:2rem;text-align:center;margin-bottom:1rem;display:none}
.result-box.show{display:block;animation:pop .35s cubic-bezier(.34,1.56,.64,1)}
.result-value{font-size:clamp(2rem,7vw,3.5rem);font-weight:800;color:var(--green);font-variant-numeric:tabular-nums;line-height:1}
.result-formula{color:var(--dim);font-size:.95rem;margin-top:.75rem}

/* Steps */
.steps-box{background:var(--card);border:1px solid var(--border2);border-left:4px solid var(--accent);border-radius:var(--r);padding:1.25rem 1.5rem;margin-bottom:1.5rem;display:none}
.steps-box.show{display:block}
.steps-box .label{font-size:.75rem;color:var(--dim);text-transform:uppercase;letter-spacing:.06em;font-weight:600;margin-bottom:.5rem}
.steps-box ol{margin:0;padding-left:1.25rem;color:var(--text);font-size:.9rem;line-height:1.9}
.steps-box ol li{margin-bottom:.3rem}
.steps-box ol li .ans{color:var(--green);font-weight:700}

.stats-footer{text-align:center;margin:1.5rem 0;font-size:.78rem;color:var(--dim)}
.stats-footer strong{color:var(--hover);font-variant-numeric:tabular-nums}
.stat-divider{margin:0 .6rem;opacity:.4}
footer{text-align:center;padding:1.5rem 2rem;color:var(--dim);font-size:.75rem;border-top:1px solid var(--border)}
footer a{color:var(--hover);text-decoration:none}
.seo-section{color:var(--dim);font-size:.88rem;margin-top:2.5rem;line-height:1.8}
.seo-section h2{color:var(--text)}

@keyframes pop{0%{transform:scale(.92);opacity:0}100%{transform:scale(1);opacity:1}}

@media(max-width:760px){
  main{padding:2rem 1.25rem 3rem}
  .tool-card{padding:1.5rem 1.25rem}
  h1{font-size:1.7rem}
  .navbar{padding:.75rem 1.25rem}
  .input-line input{width:100px;font-size:1rem}
  .calc-question{font-size:1rem}
}