#gameblock {
    position: relative;
    width: 100%;
    max-width: 640px;
    height: 100%;
    overflow: hidden;
    /* center the game block */
    margin: 0 auto;
}

header {
    /* center the game block */
    text-align: center;
}

#gamecontrol {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 40px;
    z-index: 1;
    /* center */
    display: flex;
    justify-content: center;
}

#gamearea {
    position: relative;
    top: 40px;
    left: 0;
    width: 100%;
    z-index: 0;
    display: inline;
}

#btt {
    width: 100%;
    height: 80px;
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    grid-template-rows: 1fr;
    justify-items: center;
    align-items: center;
}

#displayg {
    display: grid;
    width: 100%;
    grid-template-columns: repeat(7, 1fr);
    grid-template-rows: repeat(6, 1fr);
    border-color: black;
    border-style: solid;
    border-width: 1px;
    background-color: #0000ff;
    justify-items: center;
    align-items: center;
}

.gbtt {
    width: 60px;
    height: 60px;
    border-radius: 30px;
}

.gbttred {
    background-color: #ff0000;
}
.gbttyel {
    background-color: yellow;
}

.ddcircle {
    width: 60px;
    height: 60px;
    margin: 10px;
    border-radius: 30px;
    border-color: black;
    border-style: solid;
    border-width: 1px;
}

/* without ddcircleValid class */
.ddcircle:not(.ddcircleValid) {
    background-color: #ffffff;
}