* {
  box-sizing: border-box;
}

body.system-donate-page {
  margin: 0;
  min-height: 100vh;
  font-family: "Prompt", "Sarabun", sans-serif;
  background: #f3ecdf;
  color: #1f2f4f;
}

.donate-back-btn {
  position: fixed;
  top: 18px;
  left: 18px;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: #ffffff;
  color: #3b4f9e;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  box-shadow: 0 8px 20px rgba(31, 47, 79, 0.16);
}

.donate-stage {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 40px 16px;
}

.donate-card {
  width: min(420px, 100%);
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 18px 44px rgba(28, 40, 62, 0.28);
  overflow: hidden;
}

.donate-card-head {
  background: #3f4f9a;
  color: #fff;
  padding: 18px 20px 16px;
}

.donate-card-head h1 {
  margin: 0 0 6px;
  font-size: 25px;
  line-height: 1.2;
}

.donate-card-head p {
  margin: 0;
  font-size: 14px;
  opacity: 0.92;
}

.donate-form {
  padding: 18px 20px 22px;
}

.preset-list {
  display: grid;
  gap: 10px;
  margin-bottom: 16px;
}

.preset-item {
  width: 100%;
  border: 1px solid #e0e5f2;
  background: #fff;
  border-radius: 10px;
  color: #1f2f4f;
  font-size: 30px;
  font-weight: 700;
  padding: 12px 14px;
  text-align: left;
  cursor: pointer;
}

.preset-item.is-active {
  background: #f0f3fd;
  border-color: #3f4f9a;
  color: #2a3b78;
}

.amount-label {
  display: block;
  font-size: 14px;
  margin-bottom: 8px;
  color: #4d5c85;
}

#amountInput {
  width: 100%;
  border: 1px solid #d7deef;
  border-radius: 10px;
  padding: 12px 14px;
  font-size: 18px;
  color: #1f2f4f;
}

#amountInput:focus {
  outline: none;
  border-color: #3f4f9a;
  box-shadow: 0 0 0 3px rgba(63, 79, 154, 0.16);
}

.error-text {
  margin: 10px 0 0;
  color: #b3261e;
  font-size: 13px;
}

.submit-btn {
  margin-top: 16px;
  width: 100%;
  border: 0;
  border-radius: 10px;
  background: #f4c948;
  color: #2b2b2b;
  font-size: 20px;
  font-weight: 700;
  padding: 12px 16px;
  cursor: pointer;
}

.submit-btn:hover {
  filter: brightness(0.98);
}