* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  padding: 60px 20px;
}

.container {
  max-width: 800px;
  margin: 0 auto;
}

/* ===================================
           FORM CONTAINER
           =================================== */
.form-container {
  background-color: white;
  border-radius: 20px;
  padding: 40px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.2);
}

h1 {
  color: #1a1a2e;
  margin-bottom: 10px;
  font-size: 28px;
}

.form-description {
  color: #666;
  margin-bottom: 30px;
  padding-bottom: 20px;
  border-bottom: 1px solid #eee;
}

/* ===================================
           FORM GROUP (each field)
           =================================== */
.form-group {
  margin-bottom: 25px;
}

label {
  display: block;
  font-weight: 600;
  color: #333;
  margin-bottom: 8px;
  font-size: 14px;
}

.required {
  color: #e94560;
  margin-left: 4px;
}

/* ===================================
           INPUT STYLES (default state)
           =================================== */
input,
select,
textarea {
  width: 100%;
  padding: 12px 16px;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  font-size: 16px;
  font-family: inherit;
  transition: all 0.3s ease;
  background-color: white;
}

/* ===================================
           FOCUS STATE (when you click inside)
           =================================== */
input:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: #667eea;
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.2);
}

/* ===================================
           HOVER STATE
           =================================== */
input:hover,
select:hover,
textarea:hover {
  border-color: #aaa;
}

/* ===================================
           VALID STATE (when input is valid)
           =================================== */
input:valid,
select:valid,
textarea:valid {
  border-color: #2ecc71;
}

/* ===================================
           INVALID STATE (when input is invalid)
           =================================== */
input:invalid,
select:invalid,
textarea:invalid {
  border-color: #e74c3c;
}

/* Required field that is empty shows red border on submit attempt */
input:required:invalid,
select:required:invalid {
  border-color: #e0e0e0;
}

/* ===================================
           CHECKBOX & RADIO STYLES
           =================================== */
.checkbox-group {
  display: flex;
  align-items: center;
  gap: 10px;
}

.checkbox-group input {
  width: auto;
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.checkbox-group label {
  margin-bottom: 0;
  cursor: pointer;
  font-weight: normal;
}

/* Radio group */
.radio-group {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}

.radio-option {
  display: flex;
  align-items: center;
  gap: 8px;
}

.radio-option input {
  width: auto;
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.radio-option label {
  margin-bottom: 0;
  cursor: pointer;
  font-weight: normal;
}

/* ===================================
           BUTTON STYLES
           =================================== */
.btn-submit {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border: none;
  padding: 14px 30px;
  border-radius: 10px;
  font-size: 16px;
  font-weight: bold;
  cursor: pointer;
  width: 100%;
  transition: all 0.3s ease;
}

.btn-submit:hover {
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.btn-submit:active {
  transform: translateY(0);
}

/* ===================================
           ERROR MESSAGE STYLES
           =================================== */
.error-message {
  color: #e74c3c;
  font-size: 12px;
  margin-top: 5px;
  display: none;
}

input:invalid:focus + .error-message,
input:invalid:not(:placeholder-shown) + .error-message {
  display: block;
}

/* ===================================
           RESPONSIVE
           =================================== */
@media (max-width: 600px) {
  .form-container {
    padding: 25px;
  }

  .radio-group {
    flex-direction: column;
    gap: 10px;
  }
}

/* ===================================
           SECOND FORM EXAMPLE (inline layout)
           =================================== */
.second-example {
  margin-top: 40px;
  background-color: white;
  border-radius: 20px;
  padding: 40px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.2);
}

.inline-form {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  align-items: flex-end;
}

.inline-form .form-group {
  flex: 1;
  margin-bottom: 0;
  min-width: 150px;
}

.inline-form button {
  flex-shrink: 0;
  width: auto;
  padding: 12px 25px;
}

hr {
  margin: 40px 0;
  border-color: #eee;
}

.reference {
  background-color: #f8f9fa;
  border-radius: 12px;
  padding: 20px;
  margin-top: 30px;
}

.code {
  background-color: #1e1e2e;
  color: #82b1ff;
  padding: 15px;
  border-radius: 8px;
  font-family: "Courier New", monospace;
  font-size: 13px;
  overflow-x: auto;
}