Babylon.js/guiEditor/src/components/guiList/guiList.scss

#guiList {
    background: #333333;
    height: 100%;
    margin: 0;
    padding: 0;
    display: grid;
    width: 100%; 
    overflow: hidden;

    .panes {
        overflow: hidden;
        
        .pane {
            color: white;

            overflow: hidden;
            height: 100%;

            -webkit-user-select: none; 
            -moz-user-select: none;   
            -ms-user-select: none;    
            user-select: none;     

            .filter {
                display: flex;
                align-items: stretch;
        
                input {
                    width: 100%;
                    margin: 10px 10px 5px 10px;
                    display: block;
                    border: none;
                    padding: 0;
                    border-bottom: solid 1px rgb(51, 122, 183);
                    background: linear-gradient(to bottom, rgba(255, 255, 255, 0) 96%, rgb(51, 122, 183) 4%);
                    background-position: -1000px 0;
                    background-size: 1000px 100%;
                    background-repeat: no-repeat;  
                    color:white;    
                }
        
                input:focus  {
                    box-shadow: none;
                    outline: none;
                    background-position: 0 0;
                }

                input::placeholder {
                    color: gray;
                }
            }

            .list-container {
                overflow-x: hidden;
                overflow-y: auto;
                height: calc(100% - 32px);

                .underline {
                    border-bottom: 0.5px solid rgba(255, 255, 255, 0.5);
                }

                .draggableLine {
                    height: 30px;
                    display: grid;
                    align-items: center;
                    justify-items: stretch;
                    background: #222222;
                    cursor: grab;
                    text-align: center;
                    margin: 0;
                    box-sizing: border-box;

                    &:hover {
                        background: rgb(51, 122, 183);
                        color: white;
                    }
                }

                .nonDraggableLine {
                    height: 30px;
                    display: grid;
                    align-items: center;
                    justify-items: stretch;
                    background: #222222;
                    text-align: center;
                    margin: 0;
                    box-sizing: border-box;
                }

                .withButton {
                    height: 30px;
                    position: relative;
                    .icon {
                        position: absolute;
                        right: 4px;
                        top: 5px;
                        &:hover {
                            cursor: pointer;
                        }

                        .img {
                            height: 17px;
                            width: 17px;
                        }
                    }

                    .buttonLine {
                        height: 30px;
                        display: grid;
                        align-items: center;
                        justify-items: stretch;
                        padding-bottom: 5px;
                        position: absolute;
                        right: 0px;
                        top: 2px;
                        input[type="file"] {
                            display: none;
                        }
                
                        .file-upload {            
                            background: transparent;
                            border: transparent;
                            padding: 15px 200px;
                            opacity: 0.9;
                            cursor: pointer;
                            text-align: center;
                        }
                
                        .file-upload:hover {
                            opacity: 1.0;
                        }
                
                        .file-upload:active {
                            transform: scale(0.98);
                            transform-origin: 0.5 0.5;
                        }
                
                        button {
                            background: transparent;
                            border: transparent;
                            margin: 5px 10px 5px 10px;
                            color:white;
                            padding: 4px 5px;
                            opacity: 0.9;
                        }
                
                        button:hover {
                            opacity: 0.0;
                        }
                
                        button:active {
                            background: transparent;
                        }   
                        
                        button:focus {
                            border: transparent;
                            outline: 0px;
                        }  
                    }
                    
                }                

                .paneContainer {
                    margin-top: 3px;
                    display:grid;
                    grid-template-rows: 100%;
                    grid-template-columns: 100%;

                    .paneContainer-content {
                        grid-row: 1;
                        grid-column: 1;

                        .header {
                            display: grid;
                            grid-template-columns: 1fr auto;
                            background: #555555;    
                            height: 30px;   
                            padding-right: 5px;                        
                            cursor: pointer;
                            
                            .title {                                
                                border-left: 3px solid transparent;
                                padding-left: 5px;
                                grid-column: 1;
                                display: flex;
                                align-items: center;
                            }

                            .collapse {
                                grid-column: 2;
                                display: flex;
                                align-items: center;  
                                justify-items: center;
                                transform-origin: center;

                                &.closed {
                                    transform: rotate(180deg);
                                }
                            }                        
                        }

                        .paneList > div:not(:last-child) {
                            border-bottom: 1px solid rgba(255, 255, 255, 0.3);
                        }
                    }
                }
            }    
        }
    }
}