JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
        <li>7</li>
        <li>8</li>
        <li>9</li>
        <li>10</li>
        <li>11</li>
        <li>12</li>
        <li>13</li>
        <li>14</li>
        <li>15</li>
    </ul>
</div>

SCSS

div{
    width: 400px;
}

ul {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    flex-direction: row;
}
li {
    display: flex;
    flex-grow: 1;
    outline: 1px solid red;
    height: 100px;
    width: 100px;
    &:nth-child(-n+2) {
        outline: 1px solid blue;
        height: 50px;
    }
}