A dark theme for TheLounge IRC client inspired by Antelope Canyon (kindly shared by **ksliberal** on #thelounge @ irc.libera.chat)

thelounge-theme-canyon.css

/*
thelounge-theme-canyon
A dark theme for TheLounge IRC client inspired by Antelope Canyon

Installation instructions can be found at https://thelounge.chat/docs/server/configuration.html#theme
*/
:root {
	/* Base colors from the canyon photo */
	--canyon-orange: #FF7F38;      /* Much more vibrant orange for usernames */
	--canyon-bright: #FF6E3D;      /* Bright orange */
	--canyon-purple: #8B3B87;      /* Rich purple */
	--canyon-deep: #622c7c;        /* Deep purple */
	
	/* Additional chat colors */
	--chat-cyan: #9C4424;          /* Like +Aristos */
	--chat-bright-cyan: #9500e5;   /* Like @chalcedony */
	--chat-green: #491586;         /* Like +COBOL */
	--chat-purple: #B14FFF;        /* Like +chicken_m */
	--chat-orange: #FF8C38;        /* Like @Didache */
	--chat-system: #996633;        /* System messages */

	/* Base colors */
	--bg-hard: #1d1d1d;
	--bg: #000000;
	--bg-soft: #1a1a1a;
	--bg1: #2a2a2a;
	--bg2: #333333;
	--bg3: #404040;
	--bg4: #4d4d4d;
	--gray-245: #928374;
	--gray-244: #928374;
	--fg-hard: #ffffff;
	--fg: #f5f5f5;
	--fg-soft: #e6e6e6;
	--fg1: #d9d9d9;
	--fg2: #cccccc;
	--fg3: #bfbfbf;
	--fg4: #b3b3b3;
	--bright-red: #F90;     /* Canyon orange */
	--bright-green: #00FF9F;   /* Bright mint */
	--bright-yellow: #FFB000;  /* Warm yellow */
	--bright-blue: #FFE4FF;    /* Cyan like @chalcedony */
	--bright-purple: #FF00FF;  /* Vibrant purple */
	--bright-aqua: #9C4424;    /* Bright cyan */
	--bright-orange: #F90;  /* Canyon orange */
	--neutral-red: #A34C00;    /* Deeper orange */
	--neutral-green: #00CC7A;  /* Deep mint */
	--neutral-yellow: #FF9100; /* Deep warm yellow */
	--neutral-blue: #6B2E8B;
	--neutral-purple: #CC00CC; /* Deep purple */
	--neutral-aqua: #00CCCC;   /* Deep cyan */
	--neutral-orange: #A34C00; /* Deeper orange */
	--dim-red: #853E00;        /* Darkest orange */
	--dim-green: #009957;      /* Dark mint */
	--dim-yellow: #CC7400;     /* Dark warm yellow */
	--dim-blue: #371559;
	--dim-purple: #990099;     /* Dark purple */
	--dim-aqua: #009999;       /* Dark cyan */
	--dim-orange: #853E00;     /* Darkest orange */
	--monospace-font: "JetBrains Mono", "Fira Code", "Source Code Pro", "IBM Plex Mono", "Cascadia Code", monospace;
	--canyon-medium: #F90;  /* Deep orange midtone */
	--canyon-shadow: #8B3B87;  /* Rich purple shadow */
	--vibrant-orange: #FF6600;  /* The perfect orange from @miracles */
}

:root {
	--body-color: var(--fg1);
	--dim-color: var(--fg3);
	--link-color: var(--bright-orange);
	--window-bg-color: var(--bg);
	--body-bg-color: var(--bg);
	--active-bg-color: var(--bg1);
	--dark-bg-color: var(--bg-hard);
	--date-marker-color: var(--bright-orange);
	--unread-marker-color: var(--bright-green);
	--highlight-bg-color: var(--bright-orange);
	--highlight-border-color: var(--bright-orange);
	--overlay-bg-color: rgba(0, 0, 0, 0.7);
	--upload-progressbar-color: var(--bright-orange);
}

.user.color-1,
.user.color-17 {
	color: var(--canyon-orange);
}

.user.color-2,
.user.color-18 {
	color: var(--chat-cyan);
}

.user.color-3,
.user.color-19 {
	color: var(--canyon-purple);
}

.user.color-4,
.user.color-20 {
	color: var(--chat-bright-cyan);
}

.user.color-5,
.user.color-21 {
	color: var(--canyon-bright);
}

.user.color-6,
.user.color-22 {
	color: var(--chat-green);
}

.user.color-7,
.user.color-23 {
	color: var(--chat-purple);
}

.user.color-8,
.user.color-24 {
	color: var(--canyon-deep);
}

.user.color-9,
.user.color-25 {
	color: var(--bright-yellow);
}

.user.color-10,
.user.color-26 {
	color: var(--bright-blue);
}

.user.color-11,
.user.color-27 {
	color: var(--bright-aqua);
}

.user.color-12,
.user.color-28 {
	color: #91a6ff;
}

.user.color-13,
.user.color-29 {
	color: var(--bright-red);
}

.user.color-14,
.user.color-30 {
	color: #076678;
}

.user.color-15,
.user.color-31 {
	color: #FF7F38;
}

.user.color-16,
.user.color-32 {
	color: #499e8d;
}

html {
	scrollbar-color: var(--bg1) var(--bg);
	scrollbar-width: thin;
}

/* Borders */
#chat .content,
#chat .header,
#chat .user-mode::before,
#chat .userlist {
	border-color: var(--window-bg-color);
}

/* Button colors */
#viewport .lt,
#viewport .rt,
#chat button.menu,
#chat button.mentions,
#chat form.message-search button,
/* #chat button.search, */
#chat .count::before,
#form #submit,
#footer button {
	color: var(--link-color);
}

.btn {
	border-color: var(--link-color);
	color: var(--link-color);
}

.btn:disabled,
.btn:focus,
.btn:hover {
	background: var(--link-color);
	color: var(--body-color);
}

#viewport .lt:hover,
#viewport .rt:hover,
#chat button.menu:hover,
#chat button.mentions:hover,
#chat button.search:hover,
#form #submit:hover {
	color: var(--highlight-bg-color);
}

/* Active/hover */
.channel-list-item:hover,
.context-menu-item:focus,
.textcomplete-item:focus,
.context-menu-item:hover,
.textcomplete-item:hover,
.textcomplete-menu .active,
#chat .userlist .user.active,
#sidebar .active,
#sidebar .active:hover,
#footer button:hover {
	background-color: var(--active-bg-color);
}

/* Network-/channel list sidebar */
#sidebar {
	width: 170px;
}

@media (max-width: 768px) {
	#sidebar {
		width: 200px;
	}
}

.channel-list-item.is-muted {
	opacity: unset;
	/* the default is a bit aggressive */
}

.channel-list-item.is-muted::after {
	content: '☣';
}

.channel-list-item,
#sidebar .empty {
	color: var(--body-color);
}

.channel-list-item,
#sidebar .chan-placeholder {
	padding-bottom: 3px;
	padding-top: 3px;
}

#sidebar .network,
#sidebar .network-placeholder {
	margin-bottom: 3px;
}

#sidebar .network .collapse-network-icon::before {
	color: var(--highlight-border-color);
}

#sidebar .network .collapse-network {
	width: 35px;
	opacity: 100;
}

#sidebar .logo,
#sidebar .logo-inverted,
.channel-list-item::before,
#sidebar .channel-list-item[data-type='lobby'] .add-channel:not(.opened),
.not-secure-tooltip,
.not-secure-icon {
	display: none;
}

#sidebar .channel-list-item[data-type='lobby'],
#sidebar .not-secure .channel-list-item[data-type='lobby'] {
	color: var(--highlight-border-color);
}

.channel-list-item[data-type='lobby'].active,
.channel-list-item[data-type='lobby'] .lobby-wrap:hover,
.not-secure .channel-list-item[data-type='lobby'].active,
.not-secure .channel-list-item[data-type='lobby'] .lobby-wrap:hover {
	color: var(--highlight-bg-color);
}

/* User list sidebar */
#chat .user-mode {
	padding: 8px 0 0;
	margin-bottom: 0;
}

#chat .userlist .count {
	background: var(--body-bg-color);
}

/* Inputs */
.input,
.input:hover,
input,
#form,
#chat .userlist .search {
	color: var(--body-color);
	background-color: var(--window-bg-color);
	border-color: var(--dim-color) !important;
}

.btn:active,
.btn:focus,
.input:focus {
	border-color: rgba(0, 0, 0, 0) !important;
	box-shadow: 0 0 0 3px var(--highlight-border-color);
}

.input::placeholder,
input::placeholder,
textarea::placeholder,
#chat .userlist .search::placeholder {
	color: var(--dim-color);
}

#form {
	border: none;
}

#user-specified-css-input {
	height: 400px;
}

.password-container .reveal-password span,
#settings .extra-help,
#settings .extra-experimental {
	color: var(--highlight-border-color);
}

/* Windows */
.window {
	box-shadow: none;
}

.window h2 {
	color: var(--body-color);
}

/* Content menu */
.context-menu-item,
.textcomplete-item,
.textcomplete-item a {
	color: var(--body-color);
}

.textcomplete-menu,
#context-menu {
	background-color: var(--body-bg-color);
}

.context-menu-item::before,
.textcomplete-item::before {
	color: var(--link-color);
}

/* Channels */
#chat .chat-view[data-type='channel'] .msg.highlight {
	background: var(--body-bg-color);
	border-left: 5px solid var(--highlight-border-color);
}

#chat .chat-view[data-type='channel'] .msg.highlight .content {
	border-left: none;
}

#chat .self {
	border-left: 5px solid var(--active-bg-color);
}

#chat .self .content {
	color: var(--body-color);
}

.irc-monospace,
code {
	color: var(--body-bg-color);
	font-weight: bold;
	font-family: var(--monospace-font);
}

#chat .chat-view .notice .user,
#chat .notice .content,
#chat .notice .time,
.irc-fg2,
#chat .msg[data-type='notice'] .content,
#chat .msg[data-type='notice'] .time,
#chat .msg[data-type='notice'] .user,
#chat .msg[data-type='notice'] .from .user::before {
	color: var(--link-color) !important;
}

#chat .toggle-content {
	background: var(--body-bg-color);
	box-shadow: none;
}

#chat .toggle-text a {
	color: var(--body-color);
}

.header .topic {
	color: var(--body-color);
}

/* MOTD */
#chat .msg[data-type='motd'] .text {
	color: var(--highlight-border-color);
}

#chat .msg[data-type='motd'] .text {
	background-color: var(--dark-bg-color);
}

/* Scroll down button */
.scroll-down-arrow {
	border-color: var(--highlight-border-color);
	background-color: var(--highlight-border-color);
	color: white;
}

.scroll-down:hover .scroll-down-arrow {
	background-color: var(--highlight-bg-color);
}

.scroll-down-number {
	background-color: var(--highlight-border-color);
	color: white;
}

/* Channel list */
#chat table.channel-list td {
	color: var(--body-color);
}

/* Fileuploading */
#form #submit,
#form #upload {
	color: var(--highlight-border-color);
}

/* Image viewer */
#image-viewer.opened {
	backdrop-filter: blur(2px);
}

.mentions-popup {
	border-color: var(--highlight-bg-color);
	border-radius: 5px;
	border-style: solid;
}

.mentions-popup .msg .content {
	background-color: inherit;
}

.mentions-popup .msg .from {
	color: var(--highlight-bg-color);
}

/* Apply monospace font to all text */
body {
	font-family: var(--monospace-font);
}

/* Messages */
#chat .content {
	font-family: var(--monospace-font);
}

/* Input box */
#input {
	font-family: var(--monospace-font);
}

#sidebar .empty, .channel-list-item {
    font-size: 12px;
}