Shiny Gridster dynamicly adjust margin sizes - r

Question

I am using the 'Add-on package for using the Gridster library with Shiny', (https://github.com/wch/shiny-gridster), which is downloadable by using the below:
devtools::install_github("wch/shiny-gridster")
But I would like the size of the gridster items to be able to vary with the a slider in the sidebar.
Any help would be much appreciated.
One other question I have is how do I adjust the css for the gridsterItems so that they have all a different background, e.g. a blue background.
My ui.R and server.R can be seen below, but the gridster items do not seem to change in size in line with the slider.
First my ui.R file
# ui.R
library(shinyGridster)
library(shinydashboard)
dashboardPage(
dashboardHeader(),
dashboardSidebar(
sliderInput("n1", "gridster_box_size:", min = 50, max = 500, value = 300)
),
dashboardBody(
uiOutput('gg')
)
)
and my server.R file
# sever.R
library(shinyGridster)
shinyServer(function(input, output, session) {
output$myPlot <- renderPlot({plot(1:5)})
output$myText <- renderText(({'hello test text'}))
output$gg <- renderUI({
gridster(width = input$n1, height = input$n1,
gridsterItem(col = 1, row = 1, sizex = 1, sizey = 1,
sliderInput("n", "Input value:", min = 0, max = 50, value = 10)
),
gridsterItem(col = 2, row = 1, sizex = 1, sizey = 1,
textOutput("myText")
),
gridsterItem(col = 1, row = 2, sizex = 2, sizey = 1,
plotOutput("myPlot", height = 200)
)
)
})
}
)
A working version of gridster looks like the below for ui.R :
# ui.R
library(shinyGridster)
library(shinydashboard)
dashboardPage(
dashboardHeader(),
dashboardSidebar(
sliderInput("n1", "gridster_box_size:", min = 50, max = 500, value = 300)
),
dashboardBody(
gridster(width = 300, height = 300,
gridsterItem(col = 1, row = 1, sizex = 1, sizey = 1,
sliderInput("n", "Input value:", min = 0, max = 50, value = 10)
),
gridsterItem(col = 2, row = 1, sizex = 1, sizey = 1,
textOutput("myText")
),
gridsterItem(col = 1, row = 2, sizex = 2, sizey = 1,
plotOutput("myPlot", height = 200)
)
)
)
)
with its complementary server.R
# sever.R
library(shinyGridster)
shinyServer(function(input, output, session) {
output$myPlot <- renderPlot({plot(1:5)})
output$myText <- renderText(({'hello test text'}))
}
)