My current CSS theme for Logseq

custom.css

/* adapted from https://gist.github.com/jenningsb2/c046638de24287cb61c6d19fb611c961 */

@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:ital@0;1&family=IBM+Plex+Sans+Condensed:ital@0;1&family=IBM+Plex+Sans:ital,wght@0,100;0,400;0,700;1,100;1,400;1,700&family=IBM+Plex+Serif:ital@0;1&display=swap');

:root {
    --highlight-color: #ffdb8a;
}

/* Tags */
a.tag {
    border: 1px solid currentColor;
    background-color: var(--ct-block-reference-background);
    padding: 0 4px;
    border-radius: 4px;
    font-weight: 400;
}

a.tag[data-ref="important"],
a.tag[data-ref="wichtig"] {
    color: #df5823;
}

/* Formatting the Tasks */

.form-checkbox {
    border-radius: 10px;
    border: 2px solid var(--ls-link-text-color);
    background-color: #9cccff;
}

.waiting>.form-checkbox {
    border: 2px solid var(--highlight-color);
    background-color: #fff0ce;
}

.task-status.block-marker.waiting {
    color: #e0a210;
    border: 1px solid currentColor;
    border-radius: 4px;
    font-weight: 600;
    padding: 0 4px;
    margin-right: 4px;
}

.marker-switch.block-marker.DOING,
.marker-switch.block-marker.TODO,
.marker-switch.block-marker.LATER {
    color: var(--ls-link-text-color);
    border: 1px solid currentColor;
    border-radius: 4px;
    font-weight: 600;
    padding: 0 4px;
    margin-right: 4px;
}

a.tag:hover {
    background-color: var(--ct-block-reference-background-hover);
}

/* Fixing the div line */

hr {
    margin-top: 0.8rem;
    margin-bottom: 2rem;
}

/* Adding a custom font */

html,
body,
div,
textarea {
    font-family: "IBM Plex Sans", sans-serif;
}

.editor-inner .uniline-block:is(.h1,.h2,.h3,.h4,.h5,.h6),
h1, h2, h3, h4, h5, h6 {
    font-family: "IBM Plex Serif", serif;
}

h1.title * {
    font-family: "IBM Plex Sans Condensed", sans-serif !important;
}

/* block ref adjustments—making it easier to see them */

.block-ref {
    border-bottom: 1px solid var(--highlight-color);
    font-style: italic;
    background-color: var(--ls-secondary-background-color);
}

.white-theme,
html[data-theme="light"] {
    --ls-link-text-color: #006adc;
    --ls-link-ref-text-color: #006adc;
}

mark {
    background: var(--highlight-color);
}

/* This allows for youtube videos to be viewed in a wider screen */

@media (min-width: 800px) {
    .cp__sidebar-main-content[style*="wide"] iframe[id*="youtube-player-"] {
        height: 400px !important;
    }
}

@media (min-width: 1000px) {
    .cp__sidebar-main-content[style*="wide"] iframe[id*="youtube-player-"] {
        height: 500px !important;
    }
}

@media (min-width: 1200px) {
    .cp__sidebar-main-content[style*="wide"] iframe[id*="youtube-player-"] {
        height: 600px !important;
    }
}