Here is the styleplus. css file from skn5_maskin02 for GuppY 5.03.XX,
it is deliberately reduced to the bare necessities.

 

/*  ---------  CSS skn5_maskin02 generated update Décembre 2019 ----------- */
	  
@media screen and (max-width: 760px), screen and (max-device-width: 760px) {

#paranav { display:none;}
#returnOnTop { display:none;}
#page {
 width:100%;
 max-width:100%;
 padding:0;
 border:0;
 border-radius:0;
}
#header {
 height:0;
}
#TopBoxes, #MainContent, #CenterBoxes, #EditoBoxes,#LeftBoxes, #RightBoxes, #BlogLeftBoxes, #BlogRightBoxes { height: 100%;}
#MainContent {
 margin:0;
 background-color:#FFF;
 padding:0;
 border:0;
 border-radius:0;
 -webkit-flex-direction: column;
 flex-direction: column; 
}
#LeftBoxes, #RightBoxes, #BlogLeftBoxes, #BlogRightBoxes {
 width:100%;
 max-width:100%;
 margin: 0 auto;
 background-color:#FFF; 
}
div.logo {
 margin: 3em auto;
 padding: 0 4em;
 border-radius:0;
}
div.menuIcons ul {
 margin: 1em auto;
 width:100%;
 background:none;
 border:none;
 box-shadow:none;
 height:auto;
 padding:0;
 text-align:center;
}
div.menuIcons ul li {
 float:none;
 display:inline-block;
 margin:0 auto;
}
div.menuIcons ul li.menu_admin, div.menuIcons ul li.menu_stats {
 display: none;
}
div.menuIcons .menuIcons_flag a img {
 margin: -50px 10px 0 10px;
}
div.menuIcons ul li.menu_connect {
 position:inherit;
 float:none;
}
div.menuIcons ul li.menu_connect a span {
 background-color:#244459;
 color:#FFF;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 font-size:1em;
 font-weight:bold;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
div.menuIcons ul li.menu_connect a span.current {
 background-color:#60C4EA;
 color:#FFF;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
div.menuIcons ul li.menu_connect a:hover span {
 background-color:#B4EBFA;
 color:#000;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
div.menuIcons ul li a span {
 background-color:#244459;
 color:#FFF;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 font-size:1em;
 font-weight:bold;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
div.menuIcons ul li a span.current {
 background-color:#60C4EA;
 color:#FFF;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
div.menuIcons ul li a:hover span {
 background-color:#B4EBFA;
 color:#000;
 margin:.5em;
 padding:.5em;
 width:8.5em;
 letter-spacing:0;
 border: .1em solid #FFFFFF;
 border-radius:6px;
}
.titrebox  {
 width:100%;
 max-width:100%;
 white-space: normal;
 word-wrap:break-word;
 margin:1em auto;
 padding:1em .5em;
 letter-spacing: 0;
 border-radius:0;
}
.tblbox,.tblboxover, .box, .box a {
 width:100%;
 max-width:100%;
 font-size: 1em;
 margin: 0 auto;
 padding:.5em .5em 1em;
 }	  
.titre, .titre a {
 width:100%;
 max-width:100%;
 white-space: normal;
 word-wrap:break-word;
 margin:1em auto;
 padding:1em .5em;
 letter-spacing: 0;
 border-radius:0;
}
.tbl, .tblover {
 width:100%;
 max-width:100%;
 font-size: 1em;
 margin:0 auto;
 padding:0 .2em;
}
.TrCALBG0, .CALBG0 {
 display: none;
}
.forum, .forum a, .forum2, .forum2 td, tr.forum2  {
 font-size: 1em;
}
.quest {
 font-size: 1em;
 background-color:#B4EBFA;
}
.rep {
 font-size: 1em;
 background-color: #FFF;
}
.bord { border:0;}
ul.item li.item, .curr_item, ul.item li.curr_item a, .item, .item a  {
 font-size: 1em;
 padding:.5em 0;
}
.rubr, p.rubr, .lirubr, .lirubr2, .phrubr, .phrubr2, .farubr, .farubr2, .dnrubr, .dnrubr2  {
 margin:1em 0;
 font-size: 1em;
}
#gytabs li {
 width: 95%;
 line-height: 1.5em;
 margin: .5em 0;
}
.ariane {
 background-color:#FFF;
 padding:.5em 0;
}
#BottomBoxes {
 padding:0;	
 box-shadow:none;
}
#BottomBoxes .titrebox, #BottomBoxes .titre {
 margin:1em 0;
 padding:1em .5em;
 border:none;
}
#BottomBoxes .tblbox, #BottomBoxes .tbl {
 margin:.5em 0;
 padding:.5em;
 border:none;
 border-radius:0;	
}
#footer, .copyright, a.copyright, .timer {
 width:100%;
 color:#FFF;
 background-color:#244459;
 padding-bottom: 1em;
}
.top {
 color:#FFF;	
 padding-right: 1em;
 float: right;
}
.timer {
 display: none;
}
.copyright {
 font-size:.8em;
}
}