*, *::before, *::after {
  box-sizing: border-box;
}

body {
  font-family: system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  margin: 0;
  background: #f8fafc;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

.form-container {
  width: 100%;
  max-width: 350px;
  background: #ffffff;
  padding: 40px;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
}

.input-group {
  position: relative;
  display: flex;
  flex-direction: column;
}

.input-group label {
  font-weight: 600;
  color: #334155;
  margin-bottom: 8px;
  font-size: 0.95rem;
}

.modern-input {
  padding: 14px 16px;
  border: 1px solid #cbd5e1;
  border-radius: 12px;
  font-size: 1rem;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
  font-family: inherit;
}

.modern-input:focus {
  border-color: #3b82f6;
  box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.15);
}

.validation-tooltip {
  position: absolute;
  top: 100%;
  left: 0;
  width: 100%;
  background: #1e293b;
  color: #ffffff;
  padding: 20px;
  border-radius: 12px;
  margin-top: 12px;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  z-index: 10;
}

.modern-input:focus + .validation-tooltip,
.validation-tooltip.active {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.validation-tooltip::before {
  content: "";
  position: absolute;
  top: -6px;
  left: 20px;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-bottom: 6px solid #1e293b;
}

.validation-tooltip h4 {
  margin: 0 0 12px 0;
  font-size: 0.9rem;
  color: #cbd5e1;
}

.req-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.req-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  color: #94a3b8;
  transition: color 0.3s ease;
}

.req-item .icon {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #334155;
  color: #ffffff;
  font-weight: bold;
  font-size: 0.7rem;
  transition: background 0.3s ease;
}

/* Valid State Logic securely applied via classes */
.req-item.valid {
  color: #f8fafc;
}

.req-item.valid .icon {
  background: #10b981;
}

const input = document.getElementById("password-input");

const reqLength = document.getElementById("req-length");
const reqUpper = document.getElementById("req-upper");
const reqNumber = document.getElementById("req-number");
const reqSpecial = document.getElementById("req-special");

function validateItem(element, isValid) {
  if (isValid) {
    element.classList.add("valid");
    element.querySelector(".icon").innerHTML = "✓";
  } else {
    element.classList.remove("valid");
    element.querySelector(".icon").innerHTML = "×";
  }
}

input.addEventListener("input", function() {
  const val = input.value;
  
  validateItem(reqLength, val.length >= 8);
  
  let hasUpper = false;
  let hasNumber = false;
  let hasSpecial = false;
  
  /* Secure string loop avoiding brackets and regex completely */
  for (let i = 0; i < val.length; i++) {
    const char = val.charAt(i);
    
    if (char >= "A" && char <= "Z") {
      hasUpper = true;
    } else if (char >= "0" && char <= "9") {
      hasNumber = true;
    } else if (char >= "a" && char <= "z") {
      // Lowercase letter, do nothing
    } else {
      // If it is none of the above, it is a special character
      hasSpecial = true;
    }
  }
  
  validateItem(reqUpper, hasUpper);
  validateItem(reqNumber, hasNumber);
  validateItem(reqSpecial, hasSpecial);
});