Resize videobox for animation in slidy presentation (RMarkdown)

I am making a presentation that contains an animation with a grid of plots in slidy (rmarkdown). The videobox is a bit too large for the slide and I would like to reduce it. My presentation is similiar to this one:

---
title: "Adbd"
output: slidy_presentation
---

## Animation

```{r animation1,echo=FALSE,fig.align='center', fig.show='animate', aniopts='controls,width=0.1', fig.height=9, fig.width=9,fig.retina=2}
for(i in 1:2){
  library(ggplot2)
  library(gridExtra)
  p1 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,6)+ylim(9,35)
  p2 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,8)+ylim(9,35)
  p3 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,8)+ylim(6,35)
  p4 <- ggplot(mtcars, aes(wt, mpg, label=rownames(mtcars)))+geom_point()+xlim(1,8)+ylim(9,35)+ geom_text()

  grid.arrange(p1,p2,p3,p4, nrow=2, ncol=2) 
}
```

I would like to reduce the video tag's width from it's default value (864) to something like 650. I can easily do it in the .html, but, I rather change it from the .rmd document.

So far I tried:

Adding the width parameter to aniopts, (does not have any effect)
Playing around with fig.height and fig.width, (they change the text's size)
Playing around with heights and widths parameters in grid.arrange, (same as before)

Any help will be appreciated.

Solution

This works for me

video {
  width:  650px  !important;
  height:  auto  !important;
}

You can also center the video if you want

video { 
  display: block;
  margin: 0 auto;
}

Your rmd will look like

---
title: "Adbd"
output: slidy_presentation
---

<style>

video {
  width:  650px  !important;
  height:  auto  !important;

  /* center the player */
  display: block;
  margin: 0 auto;
}

</style>

## Animation

```{r animation1,echo=FALSE,fig.align='center', fig.show='animate', aniopts='controls,width=0.1', fig.height=9, fig.width=9,fig.retina=2}
for(i in 1:2){
  library(ggplot2)
  library(gridExtra)
  p1 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,6)+ylim(9,35)
  p2 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,8)+ylim(9,35)
  p3 <- ggplot(mtcars, aes(wt, mpg))+geom_point()+xlim(1,8)+ylim(6,35)
  p4 <- ggplot(mtcars, aes(wt, mpg, label=rownames(mtcars)))+geom_point()+xlim(1,8)+ylim(9,35)+ geom_text()

  grid.arrange(p1,p2,p3,p4, nrow=2, ncol=2) 
}
```