body {
  background: #f7f8fa;
  font-family: 'Noto Sans KR', sans-serif;
  margin: 0;
  padding: 0;
}
.calculator {
  background: #fff;
  max-width: 420px;
  margin: 40px auto;
  padding: 28px 16px 22px 16px;
  border-radius: 12px;
  box-shadow: 0 2px 16px rgba(0,0,0,0.07);
}
form .row {
  margin-bottom: 18px;
}
label {
  font-weight: 500;
  margin-bottom: 6px;
  display: block;
}
.input-group {
  display: flex;
  align-items: center;
  margin-bottom: 7px;
}
.input-group input[type="number"] {
  width: 100%;
  padding: 10px 10px;
  font-size: 18px;
  border: 1px solid #ddd;
  border-radius: 6px;
  margin-right: 8px;
  background: #fafbfc;
}
.input-group span {
  font-size: 16px;
  color: #888;
}
.btn-group, .repay-group {
  display: flex;
  gap: 7px;
  margin-bottom: 2px;
}
.amt-btn, .period-btn, .repay-btn {
  flex: 1;
  padding: 8px 0;
  background: #f0f5f3;
  border: 1px solid #d1e1da;
  border-radius: 6px;
  font-size: 15px;
  color: #222;
  cursor: pointer;
  transition: background 0.15s, border 0.15s;
}
.amt-btn:active, .period-btn:active, .repay-btn:active {
  background: #e2f1e7;
}
.repay-btn.active {
  background: #2db400;
  color: #fff;
  border: 1.5px solid #2db400;
}
.btn-row {
  display: flex;
  gap: 10px;
}
#resetBtn, #calcBtn {
  flex: 1;
  padding: 12px 0;
  font-size: 17px;
  border-radius: 6px;
  border: none;
  cursor: pointer;
  font-weight: bold;
}
#resetBtn {
  background: #e6e6e6;
  color: #444;
}
#calcBtn {
  background: #2db400;
  color: #fff;
}
.result {
  margin-top: 26px;
  background: #f0f5f3;
  padding: 18px 12px;
  border-radius: 8px;
  font-size: 16px;
  color: #222;
  line-height: 1.7;
  word-break: keep-all;
}
.result strong {
  color: #2db400;
  font-size: 20px;
}
@media (max-width: 480px) {
  .calculator {
    max-width: 100%;
    margin: 0;
    border-radius: 0;
    box-shadow: none;
    padding: 18px 4px 12px 4px;
    min-height: 100vh;
  }
  .input-group input[type="number"] {
    font-size: 16px;
    padding: 8px 6px;
  }
  .amt-btn, .period-btn, .repay-btn {
    font-size: 14px;
    padding: 7px 0;
  }
  #resetBtn, #calcBtn {
    font-size: 15px;
    padding: 10px 0;
  }
  .result {
    font-size: 15px;
    padding: 13px 6px;
  }
}