* {
  box-sizing: border-box;
}

:root{
  --bg: #0f172a;        /* dark navy */
  --card: #0b1220;      /* deep dark */
  --soft: #111b2e;      /* input bg */
  --text: #e5e7eb;      /* light text */
  --muted: #a7b0c0;     /* muted text */
  --line: #23314f;      /* border */
  --accent: #22c55e;    /* green */
  --accent2: #38bdf8;   /* sky */
  --danger: #fb7185;    /* pink-red */
}

body{
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.wrap{
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px 14px; /* good mobile margin */
}

.card{
  width: 100%;
  max-width: 560px; /* PC view stable */
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 18px;
  box-shadow: 0 18px 45px rgba(0,0,0,.35);
}

.card__header{
  display: flex;
  gap: 14px;
  align-items: center;
  margin-bottom: 16px;
}

.badge{
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: 12px;
  font-weight: 800;
  color: var(--accent2);
}

.title{
  margin: 0;
  font-size: 1.35rem;
  letter-spacing: 0.3px;
}

.subtitle{
  margin: 3px 0 0;
  color: var(--muted);
  font-size: 0.95rem;
  line-height: 1.35;
}

.grid{
  display: grid;
  gap: 12px;
  margin: 14px 0 14px;
}

@media (min-width: 520px){
  .grid{
    grid-template-columns: 1fr 1fr;
  }
}

.field{
  display: grid;
  gap: 8px;
}

.label{
  font-size: 0.95rem;
  color: var(--text);
}

.inputbox{
  display: flex;
  align-items: center;
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow: hidden;
}

.prefix{
  padding: 10px 12px;
  color: var(--muted);
  border-right: 1px solid var(--line);
  font-weight: 700;
  min-width: 44px;
  text-align: center;
}

input{
  width: 100%;
  padding: 12px 12px;
  border: none;
  outline: none;
  background: transparent;
  color: var(--text);
  font-size: 1rem;
}

input::placeholder{
  color: #75809a;
}

.hint{
  color: var(--muted);
  font-size: 0.82rem;
}

.btn{
  width: 100%;
  border: none;
  cursor: pointer;
  padding: 12px 14px;
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 750;
  background: var(--accent);
  color: #06230f;
  transition: transform .08s ease, opacity .15s ease;
}

.btn:hover{
  opacity: .92;
}

.btn:active{
  transform: scale(.99);
}

.result{
  margin-top: 14px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding: 14px;
  background: var(--soft);
  border: 1px solid var(--line);
  border-radius: 14px;
}

.result__label{
  margin: 0;
  font-weight: 750;
}

.result__sub{
  margin: 3px 0 0;
  color: var(--muted);
  font-size: 0.85rem;
}

.result__right{
  display: flex;
  align-items: baseline;
  gap: 6px;
}

.currency{
  color: var(--muted);
  font-weight: 800;
}

.total{
  font-size: 1.55rem;
  font-weight: 900;
  letter-spacing: 0.3px;
}

.msg{
  margin: 10px 2px 0;
  min-height: 18px;
  font-size: 0.9rem;
  color: var(--muted);
}

.msg.error{
  color: var(--danger);
}