/* ===== Variables ===== */
:root {
  --color-main: #0066FF;
  --color-main-dark: #0052cc;
  --color-sax: #4da6ff;
  --color-sax-light: #a8d4ff;
  --color-white: #ffffff;
  --color-yellow: #ffe566;
  --color-text: #1a2a4a;
  --color-text-light: #4a6080;
  --font-base: "LINE Seed JP", "Hiragino Kaku Gothic ProN", "Hiragino Sans", Meiryo, sans-serif;
  --radius: 16px;
  --transition: 0.3s ease;
}

/* ===== Reset & Base ===== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-base);
  color: var(--color-text);
  line-height: 1.7;
  background-color: var(--color-white);
  -webkit-font-smoothing: antialiased;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
}

/* ===== Hero Section ===== */
.hero {
  position: relative;
  min-height: 100svh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  overflow: hidden;
}

.hero__bg {
  position: absolute;
  inset: 0;
  /* 元タイル内の格子は約120px。やや細かめのギンガムに */
  background-image: url("assets/images/bg-pattern.png");
  background-size: 1550px auto;
  background-repeat: repeat;
  z-index: 0;
}

.hero__inner {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 640px;
  padding: 0.35rem 0.35rem 0.5rem;
  text-align: center;
}

.hero__sns {
  position: relative;
  z-index: 3;
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  margin-bottom: 0;
}

.hero__sns-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--color-main);
  color: var(--color-white);
  transition:
    background-color var(--transition),
    transform var(--transition),
    box-shadow var(--transition);
}

.hero__sns-link:hover,
.hero__sns-link:focus-visible {
  background: var(--color-main-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 102, 255, 0.4);
}

.hero__sns-link:active {
  transform: translateY(0);
}

.hero__visual {
  position: relative;
  z-index: 1;
  width: calc(100% + 0.7rem);
  max-width: none;
  /* SNSとタイトルの間は詰める。円を下げる分、縦は少し確保 */
  margin: 0.2rem -0.35rem 0.85rem;
  aspect-ratio: 1 / 1.16;
  min-height: 0;
}

.hero__deco {
  position: absolute;
  object-fit: contain;
  pointer-events: none;
}

/* fusen.png は左右風船＋雲が一枚。円の手前に重ねる */
.hero__deco--fusen {
  left: 50%;
  top: 28%;
  width: 128%;
  height: 102%;
  max-width: none;
  object-fit: contain;
  transform: translate(-50%, -50%) scale(0.84);
  transform-origin: center center;
  z-index: 3;
}

.hero__photo-wrap {
  position: absolute;
  /* 初期表示の下余白を使い、円・人物を少し下へ */
  top: 63.5%;
  left: 50%;
  transform: translate(-50%, -50%);
  /* 幅・高さを別指定（iOS の abs + aspect-ratio 対策）。高さだけ少し伸ばして縦長楕円 */
  --photo-w: min(96vw, 400px);
  --photo-h: calc(var(--photo-w) * 1.07);
  width: var(--photo-w);
  height: var(--photo-h);
  border-radius: 50%;
  border: 3px solid var(--color-sax);
  background: #d6ebff;
  overflow: hidden;
  box-shadow: 0 8px 32px rgba(0, 102, 255, 0.25);
  z-index: 2;
  display: flex;
  align-items: flex-start;
  justify-content: center;
}

.hero__photo {
  /* 円を大きくしても人物の見た目サイズは維持（以前の 88vw / 360px 相当） */
  width: 100%;
  height: auto;
  max-width: none;
  flex-shrink: 0;
  /* 髪のはみ出しを抑えつつ、手まで見えるサイズ */
  transform: translateY(-9%);
  object-fit: contain;
  object-position: center top;
}

/* Happy Birthday / 名前画像は人物写真の上に重ねる（LP_MV参考） */
.hero__title-img {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 78%;
  max-width: 440px;
  height: auto;
  z-index: 5;
  pointer-events: none;
  filter:
    hue-rotate(-8deg)
    saturate(1.12)
    brightness(1.02)
    drop-shadow(2px 0 0 #fff)
    drop-shadow(-2px 0 0 #fff)
    drop-shadow(0 2px 0 #fff)
    drop-shadow(0 -2px 0 #fff)
    drop-shadow(1px 1px 0 #fff)
    drop-shadow(-1px 1px 0 #fff)
    drop-shadow(1px -1px 0 #fff)
    drop-shadow(-1px -1px 0 #fff);
}

.hero__name-img {
  position: absolute;
  bottom: -8%;
  left: 50%;
  transform: translateX(-50%);
  width: 78%;
  max-width: 440px;
  height: auto;
  z-index: 5;
  pointer-events: none;
  filter:
    drop-shadow(2px 0 0 #fff)
    drop-shadow(-2px 0 0 #fff)
    drop-shadow(0 2px 0 #fff)
    drop-shadow(0 -2px 0 #fff)
    drop-shadow(1px 1px 0 #fff)
    drop-shadow(-1px 1px 0 #fff)
    drop-shadow(1px -1px 0 #fff)
    drop-shadow(-1px -1px 0 #fff);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.hero__deco--cake {
  bottom: 0;
  left: 2%;
  width: 16%;
  z-index: 4;
  transform: rotate(-20deg);
}

.hero__deco--cracker {
  bottom: -2%;
  right: 0;
  width: 18%;
  z-index: 4;
}

.hero__date-wrap {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  margin-top: 1.7rem;
}

.hero__sweet {
  position: absolute;
  width: calc(clamp(42px, 12vw, 62px) * var(--sweet-scale, 1));
  height: auto;
  object-fit: contain;
  pointer-events: none;
  z-index: 4;
  filter: drop-shadow(0 2px 4px rgba(0, 80, 180, 0.14));
}

.hero__sweet--left {
  left: 1%;
  top: 0.55rem;
  animation: sweet-float-left 5.2s ease-in-out infinite;
}

.hero__sweet--right {
  right: 2%;
  top: 1.75rem;
  animation: sweet-float-right 6s ease-in-out infinite;
  animation-delay: -1.8s;
}

@keyframes sweet-float-left {
  0%,
  100% {
    transform: rotate(-14deg) translateY(0);
  }
  50% {
    transform: rotate(-14deg) translateY(-6px);
  }
}

@keyframes sweet-float-right {
  0%,
  100% {
    transform: rotate(11deg) translateY(0);
  }
  50% {
    transform: rotate(11deg) translateY(-7px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .hero__sweet {
    animation: none;
  }

  .hero__sweet--left {
    transform: rotate(-14deg);
  }

  .hero__sweet--right {
    transform: rotate(11deg);
  }
}

.hero__date {
  position: relative;
  display: block;
  margin: 0 auto;
  text-align: center;
  z-index: 1;
  min-width: min(88%, 19.5rem);
  padding: 0.58rem 2.4rem 0.52rem;
  font-size: clamp(1.62rem, 5.6vw, 2.35rem);
  font-weight: 800;
  color: var(--color-main);
  letter-spacing: 0.14em;
  line-height: 1.15;
  background:
    linear-gradient(135deg, rgba(255, 255, 255, 0.95), rgba(214, 235, 255, 0.95));
  border: 3px solid var(--color-main);
  border-radius: 999px;
  box-shadow:
    0 4px 0 var(--color-sax),
    0 8px 24px rgba(0, 102, 255, 0.2);
}

.hero__date::before,
.hero__date::after {
  content: "✦";
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1rem;
  color: var(--color-yellow);
  text-shadow: 0 0 6px rgba(255, 229, 102, 0.8);
}

.hero__date::before {
  left: 0.95rem;
}

.hero__date::after {
  right: 0.95rem;
}

.hero__meta {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
  margin-top: 0;
}

.hero__countdown {
  position: relative;
  z-index: 1;
  display: block;
  width: min(100%, 420px);
  padding: 0.4rem 0.75rem 0.4rem;
  background: linear-gradient(180deg, #ffffff 0%, #eef6ff 100%);
  border: 2px solid var(--color-sax);
  border-radius: 20px;
  box-shadow:
    inset 0 0 0 2px rgba(255, 255, 255, 0.9),
    0 6px 20px rgba(0, 102, 255, 0.16);
}

.hero__countdown-heading {
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--color-main);
  letter-spacing: 0.08em;
  margin-bottom: 0.25rem;
}

.hero__countdown-units {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
}

.hero__countdown-unit {
  display: flex;
  flex-direction: column;
  align-items: center;
  min-width: 4.5rem;
  padding: 0.28rem 0.35rem 0.25rem;
  background: var(--color-white);
  border: 2px solid var(--color-sax-light);
  border-radius: 14px;
  box-shadow: 0 3px 10px rgba(0, 102, 255, 0.12);
}

.hero__countdown-num {
  font-size: clamp(1.35rem, 5vw, 1.75rem);
  font-weight: 800;
  color: var(--color-main);
  line-height: 1;
  font-variant-numeric: tabular-nums;
}

.hero__countdown-label {
  margin-top: 0.25rem;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--color-text-light);
  letter-spacing: 0.05em;
}

.hero__countdown-sep {
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--color-sax);
  line-height: 1;
  padding-bottom: 0.9rem;
}

.hero__countdown[hidden] {
  display: none !important;
}

.hero__meta--birthday {
  width: 100%;
  margin-inline: auto;
  padding-bottom: 0.85rem;
}

.hero__meta--birthday .hero__date-wrap {
  margin-top: 1.15rem;
}

.hero__meta--birthday .hero__date {
  min-width: min(98%, 26.5rem);
  padding: 1.02rem 3.15rem 0.94rem;
  font-size: clamp(2.05rem, 7vw, 2.9rem);
  letter-spacing: 0.16em;
}

.hero__meta--birthday .hero__date::before {
  left: 1.3rem;
}

.hero__meta--birthday .hero__date::after {
  right: 1.3rem;
}

.hero__crackers[hidden] {
  display: none !important;
}

.hero__crackers {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  width: 100%;
  margin-top: -0.15rem;
  overflow: visible;
  pointer-events: none;
  z-index: 2;
}

.hero__crackers img {
  flex: 0 0 auto;
  width: 10.25rem;
  max-width: none;
  height: auto;
  margin: 0 -1.45rem;
  object-fit: contain;
  filter: drop-shadow(0 2px 4px rgba(0, 80, 180, 0.16));
}

.hero__crackers img:nth-child(1) {
  transform: rotate(-14deg);
}

.hero__crackers img:nth-child(2) {
  transform: rotate(-2deg);
  z-index: 1;
}

.hero__crackers img:nth-child(3) {
  transform: rotate(12deg);
}

.balloon-layer[hidden] {
  display: none !important;
}

.balloon-layer {
  position: absolute;
  inset: 0;
  z-index: 6;
  overflow: hidden;
  pointer-events: none;
}

.balloon {
  position: absolute;
  top: 0;
  width: var(--balloon-size, 60px);
  animation: balloon-rise var(--rise-duration, 18s) linear var(--rise-delay, 0s) infinite;
  will-change: transform;
}

.balloon img {
  width: 100%;
  height: auto;
  filter: drop-shadow(0 4px 8px rgba(0, 60, 140, 0.18));
  animation: balloon-sway var(--sway-duration, 3.4s) ease-in-out infinite alternate;
}

@keyframes balloon-rise {
  0% {
    transform: translateY(var(--layer-h, 100%));
    opacity: 0;
  }
  8% {
    opacity: 1;
  }
  92% {
    opacity: 1;
  }
  100% {
    transform: translateY(calc(-100% - 24px));
    opacity: 0;
  }
}

@keyframes balloon-sway {
  from {
    transform: translateX(calc(-1 * var(--sway-x, 16px))) rotate(-5deg);
  }
  to {
    transform: translateX(var(--sway-x, 16px)) rotate(5deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  .balloon-layer {
    display: none !important;
  }
}

/* ===== Sections ===== */
.section {
  padding: 2rem 1.25rem;
}

.section--concept {
  background: linear-gradient(180deg, var(--color-sax-light) 0%, var(--color-white) 100%);
}

.section--projects {
  background: var(--color-white);
}

.section--gallery {
  padding-left: 0;
  padding-right: 0;
  background: linear-gradient(
    180deg,
    var(--color-white) 0,
    var(--color-sax-light) 6.5rem,
    var(--color-sax-light) 100%
  );
}

.section--gallery .section__inner {
  padding-left: 1.25rem;
  padding-right: 1.25rem;
}

.section--contact {
  background: var(--color-white);
}

.section--faq {
  background: var(--color-sax-light);
}

.section__inner {
  max-width: 720px;
  margin: 0 auto;
}

.section__heading {
  font-size: clamp(1.4rem, 4vw, 1.85rem);
  font-weight: 800;
  color: var(--color-main);
  text-align: center;
  letter-spacing: 0.15em;
  margin-bottom: 1.25rem;
}

/* ===== Concept ===== */
.concept__theme {
  font-size: clamp(1.1rem, 3vw, 1.4rem);
  font-weight: 800;
  color: var(--color-text);
  text-align: center;
  margin-bottom: 0.4rem;
}

.concept__copy {
  font-size: 0.88rem;
  font-weight: 800;
  color: var(--color-main);
  text-align: center;
  margin-top: 1.25rem;
  margin-bottom: 0;
  line-height: 1.7;
}

.concept__message {
  font-size: 0.85rem;
  color: var(--color-text-light);
  text-align: center;
  line-height: 1.85;
}

/* ===== Project Cards ===== */
.project-card {
  background: var(--color-white);
  border: 2px solid var(--color-sax);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-bottom: 1rem;
  box-shadow: 0 4px 16px rgba(0, 102, 255, 0.08);
  transition: box-shadow var(--transition);
}

.project-card:hover {
  box-shadow: 0 6px 24px rgba(0, 102, 255, 0.15);
}

.project-card--coming-soon {
  text-align: left;
}

.project-card__title {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--color-main);
  margin-bottom: 0.6rem;
}

.project-card__desc {
  font-size: 0.95rem;
  color: var(--color-text);
  margin-bottom: 0.5rem;
}

.project-card__note {
  font-size: 0.85rem;
  color: var(--color-text-light);
  margin-bottom: 0.5rem;
  line-height: 1.75;
}

.project-card__period {
  font-size: 0.85rem;
  color: var(--color-text-light);
  margin-bottom: 0.85rem;
}

.project-card__media {
  margin: 0 0 0.85rem;
  border-radius: 12px;
  overflow: hidden;
  background: #eef5ff;
}

.project-card__media img {
  width: 100%;
  height: auto;
  display: block;
}

.project-card__notes {
  list-style: none;
  font-size: 0.85rem;
  color: var(--color-text-light);
  margin-bottom: 0.85rem;
  padding-left: 0;
}

.project-card__notes li {
  padding: 0.15rem 0;
  padding-left: 1rem;
  position: relative;
}

.project-card__notes li::before {
  content: "・";
  position: absolute;
  left: 0;
  color: var(--color-main);
}

.project-card .btn {
  display: block;
  width: fit-content;
  max-width: 100%;
  margin: 0 auto;
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  background: var(--color-main);
  color: var(--color-white);
  font-family: var(--font-base);
  font-size: 0.9rem;
  font-weight: 700;
  padding: 0.75rem 1.5rem;
  border: 2px solid var(--color-main);
  border-radius: 999px;
  cursor: pointer;
  text-align: center;
  transition:
    background-color var(--transition),
    color var(--transition),
    border-color var(--transition),
    transform var(--transition),
    box-shadow var(--transition);
}

.btn:hover,
.btn:focus-visible {
  background: var(--color-main-dark);
  border-color: var(--color-main-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(0, 102, 255, 0.35);
}

.btn:active {
  transform: translateY(0);
  box-shadow: none;
}

.btn--outline {
  background: var(--color-white);
  color: var(--color-main);
}

.btn--outline:hover,
.btn--outline:focus-visible {
  background: var(--color-main);
  color: var(--color-white);
}

/* ===== Coming Soon ===== */
.coming-soon {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--color-sax);
  letter-spacing: 0.1em;
}

.coming-soon--large {
  font-size: clamp(1.25rem, 4vw, 1.75rem);
  text-align: center;
  padding: 2.25rem 1rem;
  background: var(--color-white);
  border: 2px dashed var(--color-sax);
  border-radius: var(--radius);
}

/* ===== Gallery ===== */
.gallery__desc {
  text-align: center;
  font-size: 0.95rem;
  color: var(--color-text-light);
  margin-bottom: 0.35rem;
}

.section--gallery .gallery__hint {
  display: block;
  width: fit-content;
  max-width: 100%;
  margin: 0 auto 1rem;
  padding: 0.45rem 0.9rem;
  text-align: center;
  font-size: 0.85rem;
  font-weight: 700;
  color: #0066FF;
  background: #e8f1ff;
  border-radius: 8px;
}

.gallery-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  width: 100%;
  overflow: hidden;
}

.gallery-grid[hidden] {
  display: none;
}

.gallery-grid__item {
  position: relative;
  display: block;
  width: 100%;
  padding: 0;
  border: 0;
  background: #d7e6f8;
  cursor: pointer;
  overflow: hidden;
}

.gallery-grid__item::before {
  content: "";
  display: block;
  padding-top: 125%;
}

.gallery-grid__item img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  max-width: none;
  object-fit: cover;
  transition: transform 0.35s ease, filter 0.35s ease;
}

.gallery-grid__item:hover img,
.gallery-grid__item:focus-visible img {
  transform: scale(1.04);
  filter: brightness(1.06);
}

.gallery-grid__item:focus-visible {
  outline: 2px solid var(--color-main);
  outline-offset: -2px;
  z-index: 1;
}

.gallery-grid__new {
  position: absolute;
  top: 0.28rem;
  left: 0.28rem;
  z-index: 2;
  width: 1.15rem;
  height: 1.15rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  line-height: 1;
  color: var(--color-yellow);
  background: var(--color-main);
  border: 1.5px solid #fff;
  border-radius: 50%;
  box-shadow: 0 1px 4px rgba(0, 40, 120, 0.28);
  pointer-events: none;
}

.lightbox[hidden] {
  display: none !important;
}

.lightbox:not([hidden]) {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
}

.lightbox__backdrop {
  position: absolute;
  inset: 0;
  background: rgba(10, 22, 44, 0.88);
}

.lightbox__dialog {
  position: relative;
  z-index: 1;
  width: 100%;
  height: 100%;
}

.lightbox__figure {
  position: absolute;
  top: 3.5rem;
  right: 0.75rem;
  bottom: 2.75rem;
  left: 0.75rem;
  z-index: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0;
  min-width: 0;
  pointer-events: none;
}

.lightbox__img {
  display: block;
  width: auto;
  height: auto;
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.45);
  pointer-events: auto;
}

.lightbox__close,
.lightbox__nav {
  position: absolute;
  z-index: 2;
  border: 0;
  background: rgba(255, 255, 255, 0.28);
  color: var(--color-white);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  transition: background-color var(--transition), transform var(--transition);
}

.lightbox__close:hover,
.lightbox__close:focus-visible,
.lightbox__nav:hover,
.lightbox__nav:focus-visible {
  background: rgba(255, 255, 255, 0.4);
}

.lightbox__close {
  top: 0.7rem;
  right: 0.7rem;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  font-size: 1.6rem;
  line-height: 1;
}

.lightbox__nav {
  top: 50%;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  font-size: 2rem;
  line-height: 1;
  transform: translateY(-50%);
}

.lightbox__nav--prev {
  left: 0.35rem;
}

.lightbox__nav--next {
  right: 0.35rem;
}

.lightbox__counter {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0.7rem;
  z-index: 2;
  text-align: center;
  color: rgba(255, 255, 255, 0.85);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.06em;
}

body.lightbox-open {
  overflow: hidden;
}

body.lightbox-open .back-to-top {
  visibility: hidden;
}

body.lightbox-open .balloon-layer {
  visibility: hidden;
}

/* ===== Contact ===== */
.contact__desc {
  text-align: center;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 1rem;
}

.contact__notice {
  margin-top: 1.15rem;
  font-size: 0.85rem;
  color: var(--color-text-light);
  line-height: 1.8;
  padding: 0.9rem;
  background: #f0f6ff;
  border-radius: var(--radius);
  border-left: 4px solid var(--color-main);
}

.section--contact .btn {
  display: block;
  width: fit-content;
  max-width: 100%;
  margin: 0 auto;
}

/* ===== FAQ ===== */
.faq-item {
  background: var(--color-white);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-bottom: 0.85rem;
  box-shadow: 0 4px 16px rgba(0, 102, 255, 0.08);
}

.faq-item:last-child {
  margin-bottom: 0;
}

.faq-item__title {
  font-size: 1rem;
  font-weight: 800;
  color: var(--color-main);
  margin-bottom: 0.6rem;
}

.faq-item__answer {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.8;
}

/* ===== Footer ===== */
.footer {
  background: var(--color-main);
  padding: 1.25rem 1.25rem;
  text-align: center;
}

.footer__copy {
  font-size: 0.8rem;
  color: var(--color-white);
  letter-spacing: 0.05em;
}

/* ===== Back to Top ===== */
.back-to-top {
  position: fixed;
  right: 1rem;
  bottom: 1.25rem;
  z-index: 100;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-main);
  color: var(--color-white);
  border-radius: 50%;
  box-shadow: 0 4px 16px rgba(0, 102, 255, 0.35);
  transition:
    background-color var(--transition),
    transform var(--transition),
    box-shadow var(--transition);
}

.back-to-top__icon {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
}

.back-to-top__line {
  display: block;
  width: 16px;
  height: 2px;
  background: currentColor;
  border-radius: 1px;
}

.back-to-top__arrow {
  display: block;
  font-size: 1.15rem;
  font-weight: 800;
  line-height: 1;
}

.back-to-top:hover,
.back-to-top:focus-visible {
  background: var(--color-main-dark);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 102, 255, 0.45);
}

.back-to-top:active {
  transform: translateY(0);
}

/* ===== Tablet & Desktop ===== */
@media (min-width: 768px) {
  .hero {
    align-items: center;
  }

  .hero__inner {
    max-width: 820px;
    padding: 0.75rem 2rem 1.75rem;
  }

  .hero__sns {
    margin-bottom: 0.3rem;
  }

  .hero__visual {
    width: 100%;
    max-width: 760px;
    margin: 0 auto 1.15rem;
    aspect-ratio: 1.25 / 1;
    min-height: 0;
  }

  .hero__deco--fusen {
    top: 48%;
    width: 142%;
    height: 100%;
    transform: translate(-50%, -50%) scale(1.12, 1);
  }

  .hero__photo-wrap {
    --photo-w: clamp(400px, 50vw, 520px);
    top: 59.5%;
  }

  .hero__title-img {
    top: -2%;
    width: 48%;
    max-width: 480px;
  }

  .hero__name-img {
    bottom: -4%;
    width: 46%;
    max-width: 460px;
  }

  .hero__deco--cake {
    left: 16%;
    bottom: -2%;
    width: 12%;
    transform: rotate(-20deg);
  }

  .hero__deco--cracker {
    right: 14%;
    bottom: -6%;
  }

  .hero__photo {
    width: 100%;
    transform: translateY(-11%);
  }

  .hero__date-wrap {
    margin-top: 0.75rem;
  }

  .hero__date {
    min-width: 22.5rem;
    padding: 0.7rem 2.9rem 0.64rem;
    font-size: 2.45rem;
  }

  .hero__sweet {
    width: calc(clamp(52px, 6.5vw, 76px) * var(--sweet-scale, 1));
  }

  .hero__sweet--left {
    left: 5%;
    top: 0.65rem;
  }

  .hero__sweet--right {
    right: 6%;
    top: 1.85rem;
  }

  .hero__meta {
    gap: 0.3rem;
  }

  .hero__countdown {
    padding: 0.45rem 0.85rem 0.5rem;
  }

  .hero__countdown-heading {
    margin-bottom: 0.3rem;
  }

  .hero__meta--birthday {
    width: 100%;
  }

  .hero__crackers {
    margin-top: 0.1rem;
  }

  .hero__crackers img {
    width: 17.25rem;
    margin: 0 -2.15rem;
  }

  .hero__meta--birthday .hero__date {
    min-width: 30rem;
    padding: 1.18rem 3.9rem 1.08rem;
    font-size: 3.15rem;
  }

  .balloon {
    width: calc(var(--balloon-size, 60px) * 1.18);
  }

  .section {
    padding: 2.75rem 2rem;
  }

  .section--gallery {
    padding-left: 2rem;
    padding-right: 2rem;
  }

  .section--gallery .section__inner {
    padding-left: 0;
    padding-right: 0;
  }

  .gallery-grid {
    max-width: 720px;
    margin-left: auto;
    margin-right: auto;
  }

  .gallery-grid__new {
    top: 0.35rem;
    left: 0.35rem;
    width: 1.28rem;
    height: 1.28rem;
    font-size: 0.78rem;
  }

  .lightbox__figure {
    left: 4rem;
    right: 4rem;
  }

  .project-card {
    padding: 1.5rem;
  }

  .concept__message {
    font-size: 0.95rem;
  }

  .concept__copy {
    font-size: 1.05rem;
  }
}

@media (min-width: 1024px) {
  .hero__inner {
    max-width: 920px;
  }

  .hero__visual {
    max-width: 860px;
  }

  .hero__photo-wrap {
    --photo-w: clamp(460px, 52vw, 560px);
    top: 59.5%;
  }

  .section__inner {
    max-width: 800px;
  }

  .section {
    padding: 3rem 2rem;
  }

  .section--gallery {
    padding-left: 2rem;
    padding-right: 2rem;
  }

  .gallery-grid {
    max-width: 800px;
  }
}