demo.css

/* the following styling is for the demo and not necessary for the component */
:root {
    --alert-bg: #600;
    --alert-color: #eee;
    --sd-pie-bg: transparent;
    --sd-pie-fg: #f00c;
    --sd-bar-bg: #0002;
}
* { box-sizing: border-box; }
@media (prefers-color-scheme: dark) {
    :root {
        --alert-bg: #900;
        --sd-pie-fg: #f339;
        --sd-bar-bg: #fff2;
        color-scheme: dark;
    }
}

.alert {
    align-items: center;
    background-color: var(--alert-bg);
    border-radius: 3px;
    color: var(--alert-color);
    display: flex;
    flex-direction: row;
    gap: 1rem;
    justify-content: space-between;
    padding: 1rem;
}

.alert .self-destruct {
    -webkit-appearance: none;
    background-color: #fffd;
    border-radius: 50%;
    border-width: 0;
    color: #000;
    float: right;
    font-family: inherit;
    font-size: inherit;
    font-weight: bold;
    line-height: 1;
    padding: 0.5em;
    width: 2em;
    height: 2em;
}

.alert .self-destruct:focus,
.alert .self-destruct:hover {
    background-color: #ff0c;
}

body {
    font-family: Inter, Roboto, 'Helvetica Neue', 'Arial Nova', 'Nimbus Sans', Arial, sans-serif;
    height: 100%; /* needed for .toast-container */
    position: relative; /* needed for .toast-container */
}

code {
    border: 1px solid #ccc;
    border-radius: 3px;
    display: inline-block;
    font-family: 'Jetbrains Mono', ui-monospace, 'Cascadia Code', 'Source Code Pro', Menlo, Consolas, 'DejaVu Sans Mono', monospace;
    font-size: 0.9rem;
    padding: 2px 4px;
}

[progress="bar"] .self-destruct-progress {
    position: absolute;
    right: 0;
    height: 100%;
    top: 0;
    width: 100%;
}

[progress="bar"] .self-destruct-progress-bar {
    background-color: var(--sd-bar-bg);
    height: 100%;
    display: inline-block;
}

self-destruct {
    display: block;
    position: relative;
}

.self-destruct-svg {
    float: left;
    height: 1em;
    margin-bottom: -0.1em;
    margin-right: 0.5em;
    width: 1em;
}

.self-destruct-svg-bg { fill: var(--sd-pie-bg); }
.self-destruct-svg-fg { fill: var(--sd-pie-fg); }

.toast-container {
    display: flex;
    flex-direction: column;
    position: fixed;
    right: 2rem;
    top: 2rem;
    z-index: 9999;
}
.toast {
    background-clip: border-box;
    background-color: palegoldenrod;
    border: 2px solid goldenrod;
    border-radius: 2px;
    color: #222;
    font-weight: bold;
    margin-bottom: 0.5rem;
    padding: 0;
    position: relative;
    text-align: left;
    width: 20rem;
}

.toast p {
    margin: 0;
    padding: 1rem;
}

.toast .self-destruct-progress-bar {
    background-color: #0001;
}

.toast .self-destruct {
    background-color: transparent;
    border: 0;
    color: currentColor;
    font-size: 1.5rem;
    font-weight: bold;
    line-height: 1;
    padding: 0 4px;
    position: absolute;
    right: 0;
    top: 0;
    z-index: 1;
}

.toast .self-destruct:hover,
.toast .self-destruct:focus {
    color: red;
}