Vertical to Horizontal Sub-Menus - css

Question

On my website at twoguysplayingzelda.com, my sub-menus (desktop view) are currently displayed vertically and I would like to change it to horizontal. When a user hovers over the tab "GAMES", I would like the sub-menu to stretch horizontally almost like a 2nd menu bar with all the games. My menu CSS code is as below. Thanks for any help!
div.navigation.section.no-padding.bg-dark {
background: #616161;
}
.main-menu {
font-family: 'Arial', sans-serif;
font-size: 1.0em;
text-align: center;
}
.main-menu li { position: relative; }
.main-menu > li { float: left; }
.main-menu > li:before {
content: none;
display: block;
position: absolute;
right: 0;
top: 50%;
margin-top: -18px;
margin-right: -13px;
}
.main-menu > li:last-child:before { content: none; }
.main-menu > li > a {
display: block;
padding-top: 12px;
padding-bottom: 12px;
padding-left: 12px;
padding-right: 12px;
font-size: 1.0em;
color: #FFFFFF;
text-transform: uppercase;
letter-spacing: 1px;
font-weight: 400;
}
.main-menu > li:first-child > a { margin-left: 0; }
.main-menu > .has-children > a,
.main-menu > .page_item_has_children > a { padding-right: 12px; position:
relative; }
.main-menu > .has-children > a::after,
.main-menu > .page_item_has_children > a::after {
content: "";
display: none;
border: 5px solid transparent;
border-top-color: #999;
position: absolute;
z-index: 1001;
right: 29px;
top: 50%;
margin-top: -2px;
}
.main-menu li:hover > a {
cursor: pointer;
background: #01B3D9;
color: #FFFFFF; }
.main-menu > .has-children:hover > a::after,
.main-menu > .page_item_has_children:hover > a::after { border-top-color:
#fff; }
/* Sub menus --------------------------------------- */
.main-menu li ul {
position: absolute;
z-index: 10000;
display: block;
left: -9999px;
top: 10px;
-webkit-opacity: 0;
-moz-opacity: 0;
opacity: 0;
z-index: 999;
-webkit-transition: opacity 0.3s ease-in-out, top 0.3s ease-in-out;
-moz-transition: opacity 0.3s ease-in-out, top 0.3s ease-in-out;
-ms-transition: opacity 0.3s ease-in-out, top 0.3s ease-in-out;
-o-transition: opacity 0.3s ease-in-out, top 0.3s ease-in-out;
transition: opacity 0.3s ease-in-out, top 0.3s ease-in-out;
}
.is_mobile .main-menu li ul {
-webkit-opacity: 1;
-moz-opacity: 1;
opacity: 1;
display: none;
}
.main-menu > li > ul { padding-top: 20px; }
.main-menu ul li {
float: none;
display: block;
border-top: 1px solid rgba(255,255,255,0.075);
}
.main-menu ul li:first-child { border-top: none; }
.main-menu ul > .has-children::after,
.main-menu ul > .page_item_has_children::after {
content: "";
color: #FFFFFF;
display: block;
border: 6px solid transparent;
border-left-color: rgba(255,255,255,0.4);
position: absolute;
z-index: 1001;
right: 10px;
top: 50%;
margin-top: -5px;
}
.main-menu ul > .has-children:hover::after,
.main-menu ul > .page_item_has_children:hover::after { border-left-color:
#fff; }
.main-menu ul li {
display: block;
width: 240px;
background: #616161;
}
.main-menu ul a {
width: 100%;
font-size: 1.0em;
background: #616161;
display: block;
text-align: left;
font-weight: 400;
padding: 3px;
padding-left: 12px;
line-height: 130%;
color: #FFFFFF;
}
.main-menu ul a:hover {
background: #01B3D9;
color: #FFFFFF;
}
.main-menu li:hover > ul {
-webkit-opacity: 1;
-moz-opacity: 1;
opacity: 1;
left: 138.25%;
margin-left: -120px;
top: 20.44px;
}
.is_mobile .main-menu li:hover ul { display: block; }
/* Deep down --------------------------------------- */
.main-menu ul li ul {
top: 5px;
}
.main-menu ul li:hover > ul {
top: 0;
left: 240px;
margin-left: 0;
}
.main-menu ul ul li { background: #3d3d3d; }
.main-menu ul ul ul li { background: #4d4d4d; }
.main-menu ul ul ul ul li { background: #4d4d4d; }

Answer 1

FYI, your games submenu will be too large to show horizontally.
Here's how you could do it though.
Delete this:
.main-menu li {
position: relative;
}
And add this
.main-menu li ul.sub-menu {
display: flex;
position: absolute;
left: 0;
right: 0;
overflow-x: auto;
margin: 0;
}
Should look like:
You can also add
.main-menu li ul.sub-menu {
flex-wrap: wrap;
}
Which will give you this: