* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 10px;
    padding: 10px;
    background-color: white;
    color: #1e1e1e;
    font-family: Arial, sans-serif;
}

header {
    position: relative;
    display: flex;
    justify-content: center;
    width: 100%;
}

h1 {
    font-size: 4.5rem;
}

#how-to-play {
    position: absolute;
    left: 20px;
    top: 20px;
    background-color: rgb(243, 72, 72);
    height: 50px;
    width: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}
#how-to-play span{
    border: 2px solid white;
    border-radius: 50%;
    padding: 10px 14px;
}

.how-to-play-info {
    visibility: hidden;
    width: 350px;
    background-color: #3a3a3a;
    color: white;
    position: absolute;
    left: 45px;
    top: 85px;
    padding: 30px;
    opacity: 0.9;
    transition: visibility 0.2s ease;
}
.how-to-play-info ol h3{
    text-align: center;
    margin-bottom: 6px;
}
.how-to-play-info ol li {
    margin-bottom: 6px;
}

.container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    max-width: 1120px;
    width: 100%;
    /* border: 2px solid #666; */
    margin: 0 auto;
}

.grid-box {
    /* (container width - container total border(left+right) / number of grid boxes (here 16) */
    width: calc((1120px - 4px) / 16);
    height: calc((1120px - 4px) / 16);
    background-color: #ffffff;
    transition: background-color 0.1s ease, scale 0.1s ease, opacity 0.1s ease;
    border: 1px solid #666;
}
.btn-container{
    display: flex;
    align-items: center;
}
button {
    padding: 16px 20px;
    border: none;
    border-radius: 8px;
    color: #fff;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    height: 60px;
}
.color-btns{
    display: flex;
    gap: 4px;
}
#new-grid {
    background-color: #264653;
}

#new-grid:hover {
    background-color: #1b333b;
}

#default {
    background-color: #2a9d8f;
}

#default:hover {
    background-color: #21867a;
}

#clear-grid {
    background-color: #e76f51;
}

#clear-grid:hover {
    background-color: #d65a3f;
}

#darken {
    background-color: #4a4e69;
}

#darken:hover {
    background-color: #6c7083;
}

#black-clr {
    background-color: #1d3557;
}

#black-clr:hover {
    background-color: #2b4974;
}

#multi-clr {
    background-color: #3274d8;
}

#multi-clr:hover {
    background-color: #1162be
}

#clr-choice {
    background-color: #f04236;
    display: flex;
    align-items: center;
    gap: 6px;
}

#clr-choice:hover {
    background-color: #ca3227;
}

button:focus {
    outline: none;
}

button:active {
    background-color: #ff0c0c;
}

.btn-container {
    display: flex;
    gap: 10px;
}

#clr-choice input[type="color"] {
    border: none;
    cursor: pointer;
}




@media (max-width: 1138px) {
    .grid-box {
        width: calc((760px - 4px) / 16);
        /* fewer boxes or tighter layout */
        height: calc((760px - 4px) / 16);
    }

    h1 {
        font-size: 2rem;
        text-align: center;
    }
    .container{
        width: 100%;
        max-width: 760px;
        max-height: 760px;
        height: 100%;
    }
    .btn-container {
        flex-direction: column;
        align-items: center;
    }
}
@media (max-width: 778px) {
    .grid-box {
        width: calc((600px - 4px) / 16);
        /* fewer boxes or tighter layout */
        height: calc((600px - 4px) / 16);
    }

    h1 {
        font-size: 2rem;
        text-align: center;
    }
    .container{
        width: 100%;
        max-width: 600px;
        max-height: 600px;
        height: 100%;
    }
    .btn-container {
        flex-direction: column;
        align-items: center;
    }
}
@media (max-width: 619px) {
    .grid-box {
        width: calc((560px - 4px) / 16);
        /* fewer boxes or tighter layout */
        height: calc((560px - 4px) / 16);
    }

    h1 {
        font-size: 2rem;
        text-align: center;
    }
    .container{
        width: 100%;
        max-width: 560px;
        max-height: 560px;
        height: 100%;
    }
    .btn-container {
        flex-direction: column;
        align-items: center;
    }
}
@media (max-width: 500px) {
    .grid-box {
        width: calc((420px - 4px) / 16);
        /* fewer boxes or tighter layout */
        height: calc((420px - 4px) / 16);
    }

    h1 {
        font-size: 2rem;
        text-align: center;
    }
    .container{
        width: 100%;
        max-width: 420px;
        max-height: 420px;
        height: 100%;
    }
    .btn-container {
        flex-direction: column;
        align-items: center;
        padding: 1em;
        font-size: 0.7rem;
    }
}
/* Android Screen */
@media (max-width: 400px) {
    .grid-box {
        width: calc((350px - 4px) / 16);
        /* fewer boxes or tighter layout */
        height: calc((350px - 4px) / 16);
    }

    h1 {
        font-size: 2rem;
        text-align: center;
    }
    .container{
        width: 100%;
        max-width: 350px;
        max-height: 350px;
        height: 100%;
    }
    .btn-container {
        flex-direction: column;
        align-items: center;
    }
    #how-to-play {
        left: 10px;
        top: 10px;
        height: 40px;
        width: 40px;
    }
    #how-to-play span{
        padding: 8px 12px;
    }
}