s3-dark.css

body { background-color: black; }
.blocklyMainBackground { fill: #444 !important; }
/*.blocklyBlockCanvas { filter: brightness(0.9) saturate(0) !important; }*/
.blocklySvg { background-color: #222 !important; }
.blocklyFlyoutBackground { fill: #222 !important; }
.blocklyFlyout { border-right-color: #000 !important; }
.blocklyZoom image { opacity: 0.25; }
.blocklyScrollbarHandle { fill: #555 !important; }
.blocklyWidgetDiv .goog-menu { background: #555 !important; border-color: #111; }
.blocklyWidgetDiv .goog-menuitem { color: #FFF !important; }
.blocklyWidgetDiv .goog-menuitem-highlight { background-color: #999 !important; border-top: 1px solid #333; border-bottom: 1px solid #333 }
.blocklyWidgetDiv .goog-menuitem-disabled .goog-menuitem-content { color: #AAA !important; }
.scratchCategoryMenu, .blocklyToolboxDiv, [class^=selector_wrapper] { background: #333 !important; color: #EEE; }
.scratchCategoryMenuItem.categorySelected { background: #444 !important; }
[class^=menu-bar_menu-bar_] { background: #222 !important; }
[class^=sprite-selector_], [class^=stage-selector_] { background: #333 !important; color: #EEE; }
[class*=sprite-selector-item] { background: #3A3A3A !important; color: #EEE; }
[class^=selector_new-buttons]::before { background: none !important; }
[class^=sprite-info] { background: #333 !important; color: #EEE; }
[class^=gui_extension-button-container] { background: #444 !important; border-color: #222 !important; }
[class^=gui_body-wrapper] { background-color: #2E2E2E !important; }
[class*=gui_tab_] { background-color: #444 !important; border-bottom-color: #2E2E2E !important; }
[class*=gui_tab_][class*=gui_is-selected] { background-color: #555 !important;  }
[class^=asset-panel_] { background-color: #444 !important; color: #EEE; }
[class^=sound-editor_round-button] { filter: brightness(0.75) saturate(0) !important; }
[class*=button_button], [class^=sound-editor_button] { background: #555 !important; border-color: #333 !important; }
.injectionDiv, .blocklyToolboxDiv, [class^=stage_stage-wrapper], [class^=asset-panel_], [class^=sprite-selector], [class^=stage-selector] { border-color: #111 !important; }
[class^=stage_stage-wrapper-overlay] { background-color: #000; }
[class*=stage_stage-overlay-content] { border: 1px solid #333 !important; }
[class^=stage-header_stage-header-wrapper-overlay] { background-color: #000; }
[class^=react-tabs]:focus::after { display: none; }
[class^=input_input-form_], [class^=sprite-info], [class^=stage-header] { border-color: #666 !important; }
[class^=backpack_backpack-header] { background: #444; color: white; }
[class^=menu-bar_help-icon] { filter: brightness(0.5); }
.Popover-body { background: #333; border-color: #222; }
.Popover-tipShape { fill: #333; stroke: #222; }
[class^=color-picker_row-header] { color: #EEE; }
[class^=color-picker_divider] { border-color: #555; }
[class^=color-picker_swatch] { border-color: #666; }
[class^=slider_handle] { background-color: #EEE; }

/* recent changes :P */

.blocklyFlyoutButton > .blocklyText, .blocklyFlyoutLabelText {
    fill: #eed !important;
}

[class^=gui_tab] span {
    font-weight: 800;
}

[class^=gui_tab] li:not([aria-selected=true]) > span {
    color: hsla(215, 100%, 85%, 0.5) !important;
}

/* Makes block text a little easier to read. */
.blocklyDraggable > .blocklyText,
.blocklyDraggable > g > text {
    text-shadow: 1px 1px 0 rgba(0, 0, 0, 0.4);
}

[class^=button_outlined-button]:not([class*=menu-bar]):not([class*=modal]):not([class*=tag-button_active]) {
    background: #444 !important;
}

[class*=modal_modal-overlay] {
    background-color: hsla(215, 20%, 35%, 0.9);
}

[class^=prompt_body] {
    background-color: hsla(0, 0%, 90%, 0.9);
}

.blocklyFlyoutButton:hover {
    fill: hsla(215, 60%, 40%, 1) !important;
}

input {
    background: #444;
    color: #FFF !important;
}

input::placeholder {
    color: #DDD;
}

input:focus {
    box-shadow: 0 0 0 0.25rem hsla(215, 100%, 55%, 0.45) !important;
}

[class^="stage_stage-wrapper-overlay"],
[class^="stage-header_stage-header-wrapper-overlay"] {
    background-color: #222;
}

/* Menu bar */

[class^=gui_menu-bar],
[class^=modal_header] {
    background-color: hsla(215, 20%, 35%, 1);
}

[class^=menu_menu] {
    background-color: hsla(215, 20%, 35%, 1);
}

[class*=project-title-input_title-field] {
    background-color: hsla(215, 20%, 32%, 1);
    border-color: hsla(0, 0%, 0%, 0.15) !important;
}

[class*=project-title-input_title-field]:hover {
    background-color: hsla(215, 20%, 29%, 1);
}

[class*=project-title-input_title-field]:focus {
    background-color: hsla(215, 20%, 25%, 1);
}

/* Context menus */

[class*=context-menu_context-menu] {
    background-color: #555;
}

/* Libraries */

[class*=modal_modal-content],
[class^=library_library-scroll-grid] {
    background-color: #2E2E2E !important;
}

[class^=library_library-scroll-grid] > [class^=library-item_library-item] {
    background-color: #3A3A3A;
    border-color: #111;
    color: white;
}

[class^=library_library-scroll-grid] > [class^=library-item_library-item]:hover {
    border-color: hsla(215, 100%, 65%, 1);
}

[class^=library-item_featured-extension] {
    color: white !important;
}

[class^=library-item_featured-extension-metadata-detail] img {
    filter: brightness(2.0) saturate(0);
}

[class^=library-item_library-item-inset-image-container] {
    border-color: #2C2C2C;
}

[class^=library_filter-bar] {
    background-color: hsla(215, 20%, 45%, 1);
}

[class^=filter_filter-input] {
    border-color: #666;
    background: #444;
    color: #FFF !important;
    border-radius: 10rem;
}

[class^=filter_filter-input]::placeholder {
    color: #FFF !important;
}

[class*=tag-button_active] {
    background-color: hsla(30, 100%, 55%, 1) !important;
}

/* Paint editor */

[class^=tool-select-base_tool-select] {
    filter: brightness(2.0) saturate(0.25);
}