CSS
/* GENERAL SPECIFICATIONS */
html { 
	box-sizing: border-box;
}

* { 
	margin:0; 
	font: 14px Arial, Helvetica, sans-serif;
	border-collapse:collapse;
}

*, ::before, ::after {
	box-sizing: inherit;
}

body {
	background: linear-gradient(to right, #f4f7fb, #eef2f7);
	color:#e0e4cc;
}

/* HYPERLINK ANCHORS */
a {
	text-decoration: none; 
	color: #1e3a8a;
	transition: 0.3s;
}
a:hover {
	color:#2563eb;
	font-weight:bold; 
}

/* INPUT FIELDS */
* input[type=text], 
* input[type=number], 
* input[type=password], 
* select {
	width:160px;
	height:24px;
	border: 1px solid #cbd5e1;
	background:#fff;
	border-radius:4px;
	transition: box-shadow 0.3s, border 0.3s;
}

* input[type="text"]:focus, 
* input[type=number]:focus, 
* input[type=password]:focus, 
* select:focus {
	border: 1px solid #2563eb;
	box-shadow: 0 0 5px 1px rgba(37,99,235,0.3);
	outline:none;
}

* input[type=submit], 
input[type=button]{
	padding:6px 12px; 
	background:#1e3a8a; 
	color:#fff;
	border:0 none;
	cursor:pointer;
	border-radius: 5px;
	min-width:6em;
	transition:0.3s;
}

* input[type=submit]:hover, 
input[type=button]:hover{
	background-color:#2563eb;
}

* input[type=submit]:active, 
input[type=button]:active{
	background-color:#0f172a;
}

* input[type="file"] {
	display: none;
}

.file-upload {
	display: inline-block;
	margin-bottom:2em;
	padding:6px 12px; 
	background:#1e3a8a; 
	color:#fff;
	border:0 none;
	cursor:pointer;
	border-radius: 5px;
	min-width:12.3em;
	transition:0.3s;
}

.file-upload:hover{
	background-color:#2563eb;
}

/* MENU: Header */
#menu_header {
	line-height:90px; 
	margin-bottom:-1.75em;
	color:#1e3a8a;
	font-weight:bold;
}

/* MENU: Tabs */
#menu_tabs ul {
	list-style: none;
	padding: 0;
	margin: 0 0 0 1em;
}

#menu_tabs li {
	float: left;
	border-bottom-width: 0;
	margin: 0 1em 0 0;
}

#menu_tabs a {
	display: block;
	background: linear-gradient(to right, #1e3a8a, #2563eb);
	padding: .7em .8em;
	color:#fff;
	width: 9em;
	text-align: center;
	border-radius:8px 8px 0 0;
	transition:0.3s;
}

#menu_tabs a:hover {
	background: linear-gradient(to right, #2563eb, #3b82f6);
	font-weight:normal;
}

#menu_tabs #tab_selected {
	background-color: #0f172a;
	border-radius:8px 8px 0 0;
}

#menu_tabs #tab_selected a {
	color: #fff;
	font-weight: bold;
	background:#0f172a;
}

/* MENU: Logout Button */
#menu_logout {
	float:right;
	width:8em;
	margin:0;
	padding:.7em;
	background:#dc2626;
	color:#fff;
	border-radius:5px;
}

#menu_logout a {
	color:#fff;
}

#menu_logout ul {
	margin:0;
	padding:0;
	list-style:none;
	text-align:center;
}

#menu_logout ul li ul {
	margin-top:1em;
	display:none;
}

#menu_logout ul li:hover ul {
	display:block;
}

#menu_logout ul li ul li {
	margin-top:.5em;
}

/* MENU: Main Part */
#menu_main {
	height:3.5em;
	clear: both;
	padding: .4em 1em;
	line-height:2.8em;
	background: linear-gradient(to right, #0f172a, #1e293b);
	margin-bottom: 2.5em;
	box-shadow:0 2px 8px rgba(0,0,0,0.15);
}

#menu_main a {
	display:inline;
	margin: 0;
	padding: .5em 1em;
	border-right: 1px solid rgba(255,255,255,0.2);
	font-size:1.05em;
	font-weight:bold;
	color: #f8fafc;
	border-radius:4px;
	transition:0.3s;
}

#menu_main a:last-child {
	border:0;
}

#menu_main a:hover {
	color:#fff;
	background-color:#2563eb;
}

#menu_main #item_selected {
	color: #93c5fd;
}

#menu_main #item_selected:hover {
	color: #fff;
}

/* MENU: Selection Bar */
#menu_selection{
	width:100%;
	height:3em;
	margin-top: -2.5em;
	margin-bottom: 2em;
	padding: 0.7em;
	text-align:center;
	background:#dbeafe;
	color:#1e3a8a;
	font-weight:bold;
	border-bottom:1px solid #93c5fd;
}

/* CONTENT DIVs */
.content_center {
	width:75%; 
	margin:auto; 
	text-align:center;
}

.content_left {
	width:40%;
	margin: auto;
	float:left; 
	text-align:center;
}

.content_right {
	width:60%; 
	margin:auto;
	float:right; 
	text-align:center;
	border-left: 1px #cbd5e1 dashed;
}

.content_settings {
	width:40%;
	margin:auto;
}

.content_settings p {
	text-align:left;
	margin-bottom:0.1em;
}

.content_settings input[type=submit]{
	margin-top:.8em;
}

#content_hidden {
	background:#eff6ff; 
	padding:3%;
	margin-top:1em;
	margin-bottom:2em;
	display:none;
	border-radius:8px;
}

/* STANDARD TABLE */
#tb_table {
	width:90%;
	margin:auto;
	margin-bottom:3em;
	border-radius:8px;
	overflow:hidden;
	box-shadow:0 2px 10px rgba(0,0,0,0.08);
}

#tb_table td, 
#tb_table th  {
	padding:8px;
	text-align:center;
	border:1px solid #e2e8f0;
	background-color: #fff;
}

#tb_table th {
	font-weight:bold;
	background:#1e3a8a;
	color:#fff;
}

#tb_table th.title, 
#tb_table th.title a {
	font-size:15px;
	font-weight:bold;
	line-height:30px;
	background:#0f172a; 
	color:#fff;
}

#tb_table tr:nth-child(even) td {
	background-color:#f8fafc;
}

#tb_table tr.balance td {
	background-color:#dbeafe;
	font-weight:bold;
}

/* TEXT-FORMATTING */
.heading, .heading_narrow {
	margin-left:auto;
	margin-right:auto;
	margin-bottom:1.5em;
	text-align:center;
	font-weight:bold;
	font-size:1.6em;
	color:#1e3a8a;	
}

.heading_narrow {
	margin-bottom: .5em;
}

.warn {
	font-weight:bold;
	color:#dc2626;
}

.export {
	margin-bottom:2em;
	text-align:center;
}

.alert{
	padding: 12px 20px;
	width:50%;
	margin: 3em auto;
	color: #1e293b;
	background-color: #eff6ff;
	border-left: 5px solid #2563eb;
	border-radius: 6px;
	box-shadow:0 2px 8px rgba(0,0,0,0.08);
}

.content_center h1 {
	margin-top:1.5em;
	font-size:1.2em;
	color:#0f172a;
}

.content_center p, 
.content_center a {
	margin-top:.25em;
	font-weight:bold;
	color:#2563eb;
}