html, body {
  overflow-x: hidden;
  background: #f6f7fb;
}

/* =========================================================
   Toast Notification
   ========================================================= */

/* Container */
#toast-container {
  position: fixed;
  top: 1.25rem;   /* top-5 */
  right: 1.25rem; /* right-5 */
  z-index: 50;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;   /* space-y-3 */
}

/* Base toast */
.toast {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  min-width: 280px;
  max-width: 380px;
  padding: 0.75rem 1rem;
  border-radius: 0.75rem;
  border: 1px solid;
  box-shadow: 0 10px 15px -3px rgba(0,0,0,.1),
              0 4px 6px -4px rgba(0,0,0,.1);
  animation: toast-slide-in 0.3s ease-out;
}

/* Toast types */
.toast-success {
  background-color: #ecfdf5; /* green-50 */
  border-color: #bbf7d0;     /* green-200 */
  color: #166534;            /* green-800 */
}

.toast-error {
  background-color: #fef2f2; /* red-50 */
  border-color: #fecaca;     /* red-200 */
  color: #991b1b;            /* red-800 */
}

.toast-warning {
  background-color: #fffbeb; /* yellow-50 */
  border-color: #fde68a;     /* yellow-300 */
  color: #92400e;            /* yellow-800 */
}

/* Icon */
.toast-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 1.75rem;
  width: 1.75rem;
  border-radius: 9999px;
  background: #ffffff;
  font-weight: 700;
  flex-shrink: 0;
}

/* Text */
.toast-text {
  font-size: 0.875rem;
  font-weight: 500;
  line-height: 1.25rem;
}

/* Animation */
@keyframes toast-slide-in {
  from {
    opacity: 0;
    transform: translateX(30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* Delete pop-out animation (works well in grid) */
.set-delete-anim {
  transition: transform 420ms cubic-bezier(0.2, 0.8, 0.2, 1),
              opacity 360ms ease,
              filter 360ms ease;
  will-change: transform, opacity, filter;
  transform-origin: center;
}

.set-delete-anim .is-deleting {
  opacity: 0;
  transform: scale(1.04) translateY(-10px);
  filter: blur(1px);
  pointer-events: none;
}
/* =========================================================
   Study Card Flip Animation
   ========================================================= */

.study-card{
  position: relative;
  border-radius: 24px;
  border: 2px solid rgba(59,130,246,0.65);
  background: #fff;
  min-height: 320px;
  cursor: pointer;
  user-select: none;
  perspective: 1400px;
  overflow: hidden;
  box-shadow: 0 10px 30px rgba(0,0,0,0.06);
}

.study-card-inner{
  position: relative;
  width: 100%;
  min-height: 320px;
  transform-style: preserve-3d;
  transition: transform 1800ms cubic-bezier(.19,1,.22,1);
}

.study-card.is-flipped .study-card-inner{
  transform: rotateY(180deg);
}

.study-face{
  position: absolute;
  inset: 0;
  padding: 44px 48px;
  display: flex;
  align-items: center;
  justify-content: center;

  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

.study-front{
  transform: rotateY(0deg);
}

.study-back{
  transform: rotateY(180deg);
}

/* watermark */
.study-watermark{
  position: absolute;
  left: 40px;
  top: 28px;
  font-size: 86px;
  font-weight: 800;
  color: rgba(0,0,0,0.08);
  line-height: 1;
  pointer-events: none;
}

.study-content{
  width: 100%;
  max-width: 760px;
  text-align: center;
}

.study-text{
  font-size: 28px;
  font-weight: 800;
  line-height: 1.45;
  color: rgba(37,99,235,1);
}

.study-hint{
  margin-top: 22px;
  font-size: 14px;
  color: rgba(107,114,128,1);
}

@media (prefers-reduced-motion: reduce){
  .study-card-inner{ transition: none; }
}

/* ===== Rating buttons ===== */

/* Rating button loading */

.rating-btn {
  position: relative;
}

.rating-btn.is-loading {
  pointer-events: none;
  opacity: 0.85;
}

.rating-btn .rating-number.is-hidden {
  visibility: hidden; /* giữ layout, chỉ ẩn số */
}

.rating-btn .rating-spinner {
  position: absolute;
  top: 10px;          /* căn giữa vị trí số */
  left: 50%;
  transform: translateX(-50%);
  font-size: 1.25rem;
  line-height: 1;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: translateX(-50%) rotate(360deg); }
}


.rating-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  background: transparent;
  border: none;
  cursor: pointer;
}

.rating-number {
  width: 72px;
  height: 72px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  font-weight: 800;
  color: #fff;
  transition: transform 200ms ease, box-shadow 200ms ease;
}

.rating-label {
  font-size: 13px;
  font-weight: 600;
  color: #6b7280; /* gray-500 */
}

/* Hover effect */
.rating-btn:hover .rating-number {
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 10px 20px rgba(0,0,0,.15);
}

/* ===== Colors ===== */
.rating-1 .rating-number {
  background: #9c0b7d; /* purple */
}

.rating-2 .rating-number {
  background: #ff8a4c; /* orange */
}

.rating-3 .rating-number {
  background: #ffd600; /* yellow */
  color: #1f2937;      /* dark text for contrast */
}

.rating-4 .rating-number {
  background: #7fb239; /* green */
}

.rating-5 .rating-number {
  background: #00a6d6; /* blue */
}

/* Optional: focus / active */
.rating-btn:active .rating-number {
  transform: scale(0.97);
}
/* ===== Page Transition Overlay (Fade + Scale) ===== */
.page-transition {
  position: fixed;
  inset: 0;
  z-index: 9999;
  pointer-events: none;
  display: none;            /* quan trọng: không chiếm width */
  opacity: 0;
  background: rgba(255, 255, 255, 0.96); /* có thể đổi sang var(--bg) nếu bạn có */
  backdrop-filter: blur(6px);           /* nhẹ, tạo cảm giác premium */
  -webkit-backdrop-filter: blur(6px);
}

.page-transition.is-on {
  display: block;
}

.page-transition.is-enter {
  animation: pt-enter 220ms ease-out forwards;
}

.page-transition.is-exit {
  animation: pt-exit 260ms ease-in forwards;
}

/* lớp “card” nhỏ giữa màn hình để nhìn đỡ trống */
.page-transition .pt-surface {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
}

.page-transition .pt-surface > div {
  width: min(520px, calc(100vw - 48px));
  height: 120px;
  border-radius: 24px;
  background: rgba(255,255,255,0.7);
  box-shadow: 0 20px 50px rgba(0,0,0,0.08);
  transform: scale(0.985);
}

/* Fade + slight scale */
@keyframes pt-exit {
  0%   { opacity: 0; transform: scale(1); }
  100% { opacity: 1; transform: scale(1); }
}

@keyframes pt-enter {
  0%   { opacity: 1; transform: scale(1); }
  100% { opacity: 0; transform: scale(1); }
}

/* 1) Bật cross-document view transitions */
@view-transition {
  navigation: auto;
}

/* 2) Tuning cho mượt, giảm “giật/chớp” */
::view-transition-old(root),
::view-transition-new(root) {
  animation-duration: 420ms; /* tăng/giảm tuỳ bạn */
  animation-timing-function: cubic-bezier(.2,.8,.2,1);
}

@keyframes vt-old {
  from { opacity: 1; transform: scale(1); filter: blur(0px); }
  to   { opacity: 0; transform: scale(0.99); filter: blur(4px); }
}

@keyframes vt-new {
  from { opacity: 0; transform: scale(1.01); filter: blur(6px); }
  to   { opacity: 1; transform: scale(1); filter: blur(0px); }
}

/* giảm motion nếu user bật Reduce Motion */
@media (prefers-reduced-motion: reduce) {
  .page-transition.is-exit,
  .page-transition.is-enter {
    animation: none !important;
  }
  ::view-transition-old(root),
  ::view-transition-new(root) {
    animation: none !important;
  }
}


/* Skeleton base */
.skeleton {
  position: relative;
  overflow: hidden;
  background: #f3f4f6; /* gray-100 */
}

.skeleton::after {
  content: "";
  position: absolute;
  top: 0;
  left: -150%;
  width: 150%;
  height: 100%;
  background: linear-gradient(
    90deg,
    rgba(243, 244, 246, 0) 0%,
    rgba(229, 231, 235, 0.9) 50%,
    rgba(243, 244, 246, 0) 100%
  );
  animation: skeleton-shimmer 1.1s ease-in-out infinite;
}

@keyframes skeleton-shimmer {
  0% { left: -150%; }
  100% { left: 150%; }
}

/* Helpers (optional) */
.skeleton-line { }
.skeleton-box { }

/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
  .skeleton::after { animation: none; }
}