:root {
    --c-background: #ffffff;
    --c-surface: #f5f5f7;
    --c-text-primary: #1d1d1f;
    --c-text-secondary: #6e6e73;
    --c-accent-blue: #007aff;
    --ink-black: #1a1a1a;
    --pure-white: #ffffff;
    --washi-white: #fbfbfa;
    --washi-border: #e9e9e6;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", "Segoe UI", "Hiragino Kaku Gothic ProN", "Hiragino Sans", 'Noto Sans JP', "Arial", sans-serif;
    background-color: var(--c-background);
    color: var(--c-text-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}
.container { max-width: 1024px; margin: 0 auto; padding: 0 24px; }
h1, h2, h3 { font-weight: 700; margin: 0; line-height: 1.3; letter-spacing: -0.01em; }
p { margin: 0; line-height: 1.7; font-size: 1.05rem; color: var(--c-text-secondary); }
a { color: var(--c-accent-blue); text-decoration: none; }
a:hover { text-decoration: none; }

.site-header {
    position: sticky; top: 0; z-index: 2000; width: 100%;
    background-color: rgba(251, 251, 250, 0.8);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--washi-border);
}
.global-nav { display: flex; align-items: center; justify-content: flex-start; padding: 16px 0; }
.site-home-link { display: flex; align-items: center; justify-content: center; }

.home-icon-img {
    width: 100px;
    height: 28px;
    display: block;
    transition: opacity 0.2s ease;
}
.site-home-link:hover .home-icon-img { opacity: 0.7; }

.page-header { text-align: center; padding: 120px 0; }
.main-headline { font-size: clamp(2.5rem, 5vw, 3.5rem); font-weight: 700; line-height: 1.25; letter-spacing: -0.02em; margin-bottom: 24px; }
.sub-headline { font-size: clamp(1.1rem, 2.5vw, 1.25rem); font-weight: 400; color: var(--c-text-secondary); max-width: 550px; margin: 0 auto; line-height: 1.6; }

.features-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 32px; padding: 100px 0; text-align: center; border-top: 1px solid var(--washi-border); }
.feature-item .icon { color: var(--c-accent-blue); margin-bottom: 16px; }
.feature-item h3 { font-size: 1.25rem; font-weight: 600; margin-bottom: 8px; color: var(--c-text-primary); }
.feature-item p { font-size: 1rem; }
.step-section { display: flex; flex-direction: column; align-items: center; gap: 40px; padding: 100px 0; border-top: 1px solid var(--washi-border); }
.step-content { flex: 1; width: 100%; }
.step-content h2 { font-size: clamp(2rem, 5vw, 2.5rem); margin-bottom: 16px; }
.step-content p { max-width: 480px; }
.phone-mockup { flex-shrink: 0; position: relative; width: 300px; height: 608px; filter: drop-shadow(0 8px 32px rgba(0, 0, 0, 0.08)); border: 12px solid #111; border-radius: 48px; background-color: #111; overflow: hidden; }
.phone-mockup img { display: block; width: 100%; height: 100%; object-fit: cover; border-radius: 36px; }
.download-section { background: var(--c-surface); padding: 80px 40px; border-radius: 24px; text-align: center; }
.download-section h2 { font-size: clamp(1.8rem, 5vw, 2.5rem); margin-bottom: 16px; }
.download-wrapper { display: flex; flex-direction: column; align-items: center; gap: 48px; margin-top: 48px;}
.download-item { display: flex; flex-direction: column; align-items: center; }
.download-item .platform-name { font-weight: 500; color: var(--c-text-primary); font-size: 1.2rem; }

.interactive-qr-wrapper {
    position: relative;
    width: 200px;
    height: 200px;
    margin: 16px auto 16px;
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
    opacity: 0; /* 最初は非表示。アニメーション完了時に表示 */
    transition: opacity 0.5s ease;
}
.qr-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
    border-radius: 8px;
}

.store-badge-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 62px;
    transition: transform 0.2s ease, opacity 0.2s ease;
    margin-top: 16px;
}
.store-badge-link:hover {
    transform: scale(1.05);
    opacity: 0.85;
    text-decoration: none;
}
.store-badge { width: auto; }
.store-badge-link[href*="itunes.apple.com"] .store-badge { height: 50px; }
.store-badge-link[href*="play.google.com"] .store-badge { height: 62px; }

.step-actions { display: flex; flex-direction: column; gap: 16px; margin-top: 32px; padding-top: 32px; border-top: 1px solid var(--washi-border); }
.cta-button { display: inline-flex; align-items: center; justify-content: center; background-color: var(--c-accent-blue); color: #fff; text-decoration: none; border-radius: 999px; transition: background-color 0.2s ease, transform 0.2s ease; padding: 12px 28px; flex-direction: column; line-height: 1.4; gap: 2px; }
.cta-button:hover { transform: scale(1.03); background-color: #0071e3; color: #fff; }
.cta-text-main { font-size: 1rem; font-weight: 700; display: block; }
.cta-text-sub { font-size: 0.8rem; font-weight: 500; opacity: 0.9; display: block; }
.cta-button svg { width: 18px; height: 18px; transition: transform 0.2s ease; }
.cta-button:hover svg { transform: translateX(3px); }

.site-footer { text-align: center; padding: 40px 0; margin-top: 80px; background-color: var(--washi-white); border-top: 1px solid var(--washi-border); }
.footer-return-link { margin-bottom: 24px; }
.footer-copyright { font-size: 0.85rem; color: var(--c-text-secondary); opacity: 0.7; }
.scroll-reveal { opacity: 0; transform: translateY(40px); transition: opacity 0.9s ease-out, transform 0.9s ease-out; }
.scroll-reveal.is-visible { opacity: 1; transform: translateY(0); }

@media (min-width: 1024px) {
    .step-section { flex-direction: row; gap: 100px; padding: 120px 0; align-items: center; }
    .step-section:nth-child(even) { flex-direction: row-reverse; }
    .download-wrapper { flex-direction: row; align-items: flex-start; justify-content: center; gap: 80px; }
    .step-actions { flex-direction: row; }
}

@keyframes ripple-wave {
  from { transform: scale(0.5); opacity: 1; }
  to { transform: scale(6); opacity: 0; }
}
#page-top-btn { position: fixed; bottom: 30px; right: 30px; z-index: 1000; width: 56px; height: 56px; cursor: pointer; opacity: 0; visibility: hidden; transform: scale(0.8); transition: opacity 0.5s ease, visibility 0.5s ease, transform 0.5s ease; }
#page-top-btn.is-shown { opacity: 1; visibility: visible; transform: scale(1); }
.btn-icon { position: absolute; top: 0; left: 0; width: 100%; height: 100%; z-index: 2; display: flex; align-items: center; justify-content: center; border-radius: 50%; background-color: var(--ink-black); transform: scale(0); opacity: 0; transition: all 0.5s cubic-bezier(0.34, 1.56, 0.64, 1) 0.5s; }
#page-top-btn.is-shown .btn-icon { transform: scale(1); opacity: 1; }
.btn-icon svg { width: 22px; height: 22px; color: var(--pure-white); transition: all 0.3s ease; }
.ripple-container { position: absolute; top: 0; left: 0; width: 100%; height: 100%; z-index: 1; pointer-events: none;  }
.ripple-container .ripple { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border-radius: 50%; box-shadow: 0 0 1px 0px rgba(26, 26, 26, 0.3); transform: scale(0); opacity: 0; }
#page-top-btn.is-shown .ripple,
#page-top-btn.is-clicked .ripple { animation-name: ripple-wave; animation-duration: 2.5s;  animation-timing-function: cubic-bezier(0.215, 0.61, 0.355, 1); animation-fill-mode: forwards; }
#page-top-btn.is-clicked .btn-icon { transition: all 0.4s ease-in; transform: scale(0.9); opacity: 0; }