/* Tip Calculator - CSS (modern + responsive) */
:root{
  --bg:#f6f8fb; --card:#ffffff; --accent:#0066ff; --muted:#6b7280; --success:#07a087;
  --text:#0b1a2b; --radius:12px; --glass:rgba(11,26,43,0.04);
}
html[data-theme="dark"]{ --bg:#0b1220; --card:#0f1724; --accent:#1e90ff; --muted:#9aa6b2; --text:#e6eef6; --glass:rgba(255,255,255,0.03); }

body {font-family:Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial; background:var(--bg); color:var(--text); margin:0; padding:18px; -webkit-font-smoothing:antialiased; -moz-osx-font-smoothing:grayscale;}

.tip-tool{max-width:820px;margin:18px auto;}
.tool-card{background:var(--card);border-radius:var(--radius);box-shadow:0 8px 30px rgba(11,26,43,.06);overflow:hidden;}
.tool-header{display:flex;justify-content:space-between;align-items:center;padding:18px 20px;border-bottom:1px solid var(--glass);}
.tool-header h1{font-size:20px;margin:0}
.controls{display:flex;gap:8px;align-items:center}

/* Theme switch */
.switch{position:relative;display:inline-block;width:44px;height:26px}
.switch input{display:none}
.switch .slider{position:absolute;cursor:pointer;top:0;left:0;right:0;bottom:0;background:#e6eef6;border-radius:20px;transition:.25s}
.switch .slider:before{content:'';position:absolute;height:20px;width:20px;left:3px;top:3px;background:white;border-radius:50%;transition:.25s;box-shadow:0 1px 6px rgba(2,6,23,.12)}
.switch input:checked + .slider{background:var(--accent)}
.switch input:checked + .slider:before{transform:translateX(18px)}

/* Body */
.tool-body{padding:20px;display:grid;gap:12px}
.row{display:flex;flex-direction:column;gap:6px}
.row label{font-size:13px;color:var(--muted)}
.row input[type="number"], .row input[type="text"], .row select{padding:10px;border-radius:8px;border:1px solid #e6eef6;background:transparent;font-size:15px;color:var(--text)}
.tip-presets{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.tip-btn{padding:8px 12px;border-radius:8px;border:1px solid var(--glass);background:transparent;cursor:pointer;font-weight:600}
.tip-btn.active{background:var(--accent);color:#fff;border:none;box-shadow:0 8px 20px rgba(6,86,255,.12)}
.center{display:flex;gap:10px;align-items:center}
.primary-btn{position:relative;overflow:hidden;padding:12px 18px;border-radius:10px;background:var(--accent);color:#fff;border:none;cursor:pointer;font-weight:700;box-shadow:0 8px 30px rgba(6,86,255,.12)}
.secondary-btn{padding:12px 16px;border-radius:10px;background:transparent;border:1px solid var(--glass);cursor:pointer}

/* ripple */
.primary-btn:after{content:"";position:absolute;border-radius:50%;transform:scale(0);opacity:.6;background:rgba(255,255,255,0.5);transition:transform .5s,opacity .8s}

/* results */
.results{margin-top:8px;padding:14px;border-radius:10px;background:linear-gradient(180deg,rgba(0,118,255,0.03),transparent);border:1px solid var(--glass)}
.result-row{display:flex;justify-content:space-between;align-items:center;padding:6px 0;border-bottom:1px dashed rgba(0,0,0,0.03)}
.result-row:last-child{border-bottom:none}
.result-row strong{font-size:16px;color:var(--text)}

/* note */
.note{font-size:13px;color:var(--muted);margin-top:6px}

/* hidden */
.hidden{display:none}

/* responsive */
@media (max-width:640px){
  .tool-card{margin:8px}
  .tip-presets .tip-btn{flex:1}
  .center{flex-direction:column;align-items:stretch}
}