CSS <integer> Data Type - Playground Example

<!DOCTYPE html><html><head><style type="text/css">@property --count {
    syntax: "<integer>";
    inherits: false;
    initial-value: 1;
}

:root {
    --unit: 18px;
    --gap: 12px;
    --bg: #0ea5a4;
}

* {
    box-sizing: border-box;
}

.demo {
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
    padding: 24px;
    color: #0f172a;
}

h2 {
    margin: 0 0 12px 0;
    font-size: 16px;
}

.examples {
    display: flex;
    gap: var(--gap);
    align-items: center;
    margin-bottom: 12px;
}

.box {
    --count: 1;
    width: calc(var(--count) * var(--unit));
    height: 48px;
    background: linear-gradient(90deg, var(--bg), #06b6d4);
    border-radius: 8px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 700;
    transition: width 350ms ease;
    position: relative;
    min-width: 36px;
    padding: 0 8px;
}

.box::before {
    content: var(--count);
    position: relative;
    z-index: 1;
}

.box-0 {
    --count: 0;
    background: linear-gradient(90deg, #94a3b8, #64748b);
}

.box-3 {
    --count: 3;
}

.box-7 {
    --count: 7;
}

.box-hover {
    --count: 2;
    cursor: pointer;
}

.box-hover:hover {
    --count: 8;
}

.note {
    margin: 0;
    font-size: 13px;
    color: #475569;
}
</style></head><body><div class="demo">
    <h2>CSS <integer> demo</h2>
    <div class="examples">
        <div class="box box-0"></div>
        <div class="box box-3"></div>
        <div class="box box-7"></div>
        <div class="box box-hover"></div>
    </div>
    <p class="note">Hover the rightmost box to change the integer (animated).</p>
</div></body></html>