*{box-sizing:border-box}
body{margin:0;min-height:100vh;display:flex;align-items:center;justify-content:center;padding:16px;
font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;
background:linear-gradient(135deg,#6366f1,#8b5cf6 50%,#ec4899);color:#1f2340}
.card{width:100%;max-width:420px;background:#fff;border-radius:24px;padding:24px;box-shadow:0 20px 50px rgba(30,20,80,.35)}
h1{margin:0;font-size:1.6rem}
.sub{margin:4px 0 20px;color:#6b7080}
.field{display:block;margin-bottom:18px}
.field>span{display:block;font-weight:600;font-size:.85rem;color:#4b5068;margin-bottom:8px}
.input{display:flex;align-items:center;background:#f3f4fb;border-radius:14px;padding:0 14px;border:2px solid transparent}
.input:focus-within{border-color:#6366f1}
.input i{font-style:normal;color:#8a8fa8;font-size:1.3rem}
input{font:inherit;border:0;background:transparent;outline:none;width:100%}
#bill{font-size:1.6rem;font-weight:700;padding:12px 8px;text-align:right}
.tips{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}
.tips button{padding:14px 0;font-size:1.05rem;font-weight:700;border:0;border-radius:12px;background:#eef0ff;color:#4338ca;cursor:pointer;transition:.15s}
.tips button.active{background:#6366f1;color:#fff;transform:scale(1.04)}
#custom{grid-column:span 1;background:#f3f4fb;border-radius:12px;padding:0 10px;text-align:center;font-weight:600;border:2px solid transparent;min-width:0}
#custom:focus,#custom.active{border-color:#6366f1}
.stepper{display:flex;align-items:center;justify-content:space-between;background:#f3f4fb;border-radius:14px;padding:6px}
.stepper button{width:48px;height:48px;border:0;border-radius:10px;background:#fff;font-size:1.6rem;color:#4338ca;cursor:pointer;box-shadow:0 1px 4px rgba(0,0,0,.1)}
.stepper button:active{transform:scale(.92)}
output{font-size:1.5rem;font-weight:700}
.result{background:#1f2340;color:#fff;border-radius:18px;padding:20px;margin-top:6px}
.per{text-align:center;padding-bottom:14px;border-bottom:1px solid rgba(255,255,255,.15)}
.per small{display:block;color:#b9bdf5;letter-spacing:.08em;text-transform:uppercase;font-size:.75rem}
.per strong{font-size:2.8rem;color:#5eead4}
dl{margin:14px 0 0}
dl div{display:flex;justify-content:space-between;padding:4px 0}
dt{color:#b9bdf5}dd{margin:0;font-weight:600}
.reset{width:100%;margin-top:14px;padding:12px;border:0;border-radius:12px;background:#f3f4fb;color:#4b5068;font-weight:600;cursor:pointer}