.install-btn {
    position: fixed;
    right: 16px;
    bottom: calc(env(safe-area-inset-bottom, 0px) + 60px);
    z-index: 120;
    border: 1px solid rgba(255,255,255,0.14);
    border-radius: 999px;
    background: rgba(10,10,10,0.72);
    color: rgba(255,255,255,0.86);
    font-family: 'Barlow Condensed', sans-serif;
    font-size: 1.45rem;
    font-weight: 300;
    letter-spacing: 0;
    line-height: 1;
    width: 40px;
    height: 40px;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 12px 22px rgba(0,0,0,0.20);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    cursor: pointer;
    transition: transform 0.2s ease, opacity 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

body.light-mode .install-btn {
    border-color: rgba(0,0,0,0.12);
    background: rgba(255,255,255,0.82);
    color: rgba(0,0,0,0.72);
    box-shadow: 0 14px 24px rgba(0,0,0,0.10);
}

.install-btn:hover,
.install-btn:focus-visible {
    transform: translateY(-1px);
    opacity: 1;
}

.install-btn.is-hidden {
    display: none !important;
}

.install-hint {
    position: fixed;
    right: 16px;
    bottom: calc(env(safe-area-inset-bottom, 0px) + 112px);
    z-index: 119;
    width: min(280px, calc(100vw - 32px));
    border: 1px solid rgba(255,255,255,0.12);
    border-radius: 18px;
    background: rgba(10,10,10,0.84);
    color: rgba(255,255,255,0.84);
    font-family: 'M PLUS 1p', 'Barlow Condensed', sans-serif;
    font-size: 0.68rem;
    letter-spacing: 0.04em;
    line-height: 1.7;
    padding: 12px 14px;
    box-shadow: 0 18px 34px rgba(0,0,0,0.24);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    opacity: 0;
    pointer-events: none;
    transform: translateY(8px);
    transition: opacity 0.22s ease, transform 0.22s ease;
}

body.light-mode .install-hint {
    border-color: rgba(0,0,0,0.10);
    background: rgba(255,255,255,0.88);
    color: rgba(0,0,0,0.72);
    box-shadow: 0 14px 28px rgba(0,0,0,0.10);
}

.install-hint.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}

@media (min-width: 769px), (pointer: fine) {
    .install-btn,
    .install-hint {
        display: none !important;
    }
}