html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    
    display: flex;
    justify-content: center;
    align-items: center;

    background-color: #333;
    color: #fff;
    font-family: "IBM Plex Sans", Arial, sans-serif;
    font-optical-sizing: auto;
    font-weight: 600;
    font-style: normal;
    font-variation-settings:
        "wdth" 100;
}

.app {
    width: 100%;
    max-width: 500px;
    height: 100%;
    background: #000;
}

.msg-container {
    position: absolute;
    bottom: 10vh;
    left: 50%;
    transform: translateX(-50%);

    padding: 0 3rem;
    background: rgba(255,255,255,0.08);

    box-shadow:
        0 0 8px rgba(255,255,255,0.15),
        0 8px 24px rgba(0,0,0,0.8);

    animation: tapFade 1.5s ease-in-out infinite;
    cursor: pointer;
}

/* 周囲のにじみ */
.msg-container::before {
    content: "";
    position: absolute;
    inset: -40px -80px;
    background: radial-gradient(
        ellipse at center,
        rgba(255,255,255,0.12) 0%,
        rgba(255,255,255,0.06) 30%,
        rgba(0,0,0,0) 70%
    );
    filter: blur(14px);
    z-index: -1;

    animation: glowFade 1.5s ease-in-out infinite;
}

.msg {
    margin: 0;
    letter-spacing: 0.2em;
    font-size: 14px;
}

.overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    line-height: 1;
    justify-content: center;
    align-items: center;
    background: rgba(0, 0, 0, 1);
    cursor: pointer;
}

.overlay p {
    margin: 0;
    padding: 0;
    font-size: 2rem;
    color: #fff;
}

.overlay h1 {
    margin: 0;
    padding: 0;
    font-size: 5rem;
    color: #fff;
}


@keyframes tapFade {
    0% {
        opacity: 0;
        transform: translateX(-50%) translateY(0);
    }
    50% {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
    100% {
        opacity: 0;
        transform: translateX(-50%) translateY(0);
    }
}

@keyframes glowFade {
    0% {
        opacity: 0;
        filter: blur(18px);
    }
    20% {
        opacity: 1;
        filter: blur(14px);
    }
    60% {
        opacity: 1;
        filter: blur(14px);
    }
    80% {
        opacity: 0;
        filter: blur(22px);
    }
    100% {
        opacity: 0;
        filter: blur(22px);
    }
}