* { box-sizing: border-box; }
body {
  font-family: system-ui, "Segoe UI", sans-serif;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #f1f5f9;
}

.cart-btn {
  position: relative;
  background: #1e293b;
  color: white;
  border: none;
  border-radius: 12px;
  padding: 14px 28px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  overflow: hidden;
  transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 160px;
  height: 54px;
  box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1);
}

.cart-btn:hover {
  background: #334155;
  transform: translateY(-2px);
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.15);
}

.btn-content {
  display: flex;
  align-items: center;
  gap: 10px;
  transition: opacity 0.3s, transform 0.3s;
}

.icon-cart {
  width: 20px;
  height: 20px;
}

.loader {
  display: none;
  width: 24px;
  height: 24px;
  border: 3px solid rgba(255,255,255,0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  position: absolute;
}

.icon-check {
  display: none;
  width: 28px;
  height: 28px;
  color: white;
  position: absolute;
  stroke-dasharray: 24;
  stroke-dashoffset: 24;
  animation: drawCheck 0.4s forwards 0.1s;
}

/* STATE: Loading */
.cart-btn.is-loading {
  width: 54px; /* Collapse to circle */
  min-width: 54px;
  border-radius: 50%;
  background: #334155;
  cursor: default;
  transform: none;
  padding: 0;
}

.cart-btn.is-loading .btn-content {
  opacity: 0;
  transform: scale(0.5);
}

.cart-btn.is-loading .loader {
  display: block;
}

/* STATE: Added */
.cart-btn.is-added {
  width: 54px;
  min-width: 54px;
  border-radius: 50%;
  background: #22c55e; /* Green */
  cursor: default;
  padding: 0;
}

.cart-btn.is-added .btn-content,
.cart-btn.is-added .loader {
  display: none;
}

.cart-btn.is-added .icon-check {
  display: block;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

@keyframes drawCheck {
  to { stroke-dashoffset: 0; }
}

const btn = document.querySelector(".cart-btn");

btn.addEventListener("click", () => {
  // Prevent multiple clicks
  if (btn.classList.contains("is-loading") || btn.classList.contains("is-added")) return;

  // 1. Start Loading
  btn.classList.add("is-loading");

  // Simulate API request (1.5s)
  setTimeout(() => {
    // 2. Success State
    btn.classList.remove("is-loading");
    btn.classList.add("is-added");

    // 3. Reset after 2.5s so user can add again
    setTimeout(() => {
      btn.classList.remove("is-added");
    }, 2500);
  }, 1500);
});