diff --git a/16_Trade-offs.Rmd b/16_Trade-offs.Rmd
index 83173cb..d6bf0de 100644
--- a/16_Trade-offs.Rmd
+++ b/16_Trade-offs.Rmd
@@ -1,372 +1,394 @@
-# Trade-offs
-
-**Learning objectives:**
-
-- Understand the Trade-offs between S3, R6 and S4
-
-- Brief intro to S7 (the object system formerly known as R7)
-
-
-## Introduction
-
-* We have three OOP systems introduced so far (S3, S4, R6) 
-
-* At the current time (pre - S7?) Hadley recommends use S3 by default: It's simple and widely used throughout base R and CRAN.
-
-* If you have experience in other languages,  *Resist* the temptation to use R6 even though it will feel more familiar!
-
-
-## S4 versus S3 
-
-**Which functional object system to use, S4 or S3? **
-
-- **S3** is a simple and flexible system.
-   
-   - Good for small teams who need flexibility and immediate payoffs.
-   
-   - Commonly used throughout base R and CRAN 
-   
-   - Flexibility can cause problems, more complex systems might require formal conventions
-   
-
-- **S4** is a more formal, strict system. 
-
-   - Good for large projects and large teams
-   
-   - Used by Bioconductor project
-   
-   - Requires significant up front investment in design, but payoff is a robust system that enforces conventions.
-   
-   - S4 Documentation is challenging to use. 
-    
-
-
-## R6 versus S3
-
-**R6** is built on **encapsulated objects**, rather than generic functions.   
-
-
-**Big differences: general trade-offs**
-
-```{r 16-Trade-offs-4, echo=FALSE,fig.align='center'}
-knitr::include_graphics("images/16-trade-offs.png")
-```
-
-## Namespacing {-}
-
-**Where methods are found?**
-
-- in S3, **Generic functions** are **global** and live in the **global namespace**
-
-   - Advantage: Uniform API: `summary`, `print`, `predict` etc.
-   
-   - Disadvantage: Must be careful about creating new methods!  Homonyms must be avoided, don't define `plot(bank_heist)`
- 
-
-- in R6, **Encapsulated methods** are **local**: objects with a **scope**
-
-   - Advantage: No problems with homonyms:  meaning of `bank_heist$plot()` is clear and unambiguous.
-   
-   - Disadvantage: Lack of a uniform API, except by convention.
-   
-
-## Threading state {-}
-
-
-In S3 the challenge is to return a value and modify the object. 
-
-
-```{r}
-new_stack <- function(items = list()) {
-  structure(list(items = items), class = "stack")
-}
-
-push <- function(x, y) {
-  x$items <- c(x$items, list(y))
-  x
-}
-```
-
-No problem with that, but what about when we want to pop a value?  We need to return two things.
-
-```{r}
-pop <- function(x) {
-  n <- length(x$items)
-  
-  item <- x$items[[n]]
-  x$items <- x$items[-n]
-  
-  list(item = item, x = x)
-}
-```
-
-The usage is a bit awkward:
-
-```{r}
-s <- new_stack()
-s <- push(s, 10)
-s <- push(s, 20)
-
-out <- pop(s)
-# Update state:
-s <- out$x
-
-print(out$item)
-```
-
-
-In python and other languages we have structured binding to make this less awkward.  R has the {zeallot} package. For more, see this vignette:
-
-```{r 16-Trade-offs-5, eval=FALSE}
-vignette('unpacking-assignment')
-```
-
-However, this is all easier in R6 due to the reference semantics!
-
-```{r}
-Stack <- R6::R6Class("Stack", list(
-  items = list(),
-  push = function(x) {
-    self$items <- c(self$items, x)
-    invisible(self)
-  },
-  pop = function() {
-    item <- self$items[[self$length()]]
-    self$items <- self$items[-self$length()]
-    item
-  },
-  length = function() {
-    length(self$items)
-  }
-))
-
-s <- Stack$new()
-s$push(10)
-s$push(20)
-s$pop()
-```
-
-
-## Method chaining {-}
-
-Useful to compose functions from left-to-right.
-
-Use of the operators:
-
-- S3: `%>%`
-
-- R6: `$`
-
-```{r}
-s$push(44)$push(32)$pop()
-```
-
-
-## Umm... what about S7 ? {-}
-
-```{r standards, echo = FALSE,  fig.cap = "https://xkcd.com/927/"}
-
-knitr::include_graphics("https://imgs.xkcd.com/comics/standards_2x.png")
-
-```
-
-### Primary references: {-}
-
-* Docs: https://rconsortium.github.io/OOP-WG/
-
-* Talk by Hadley Wickham https://www.youtube.com/watch?v=P3FxCvSueag
-
-## S7 briefly {-}
-
-* S7 is a 'better' version of S3 with some of the 'strictness' of S4.
-
-```
-"A little bit more complex then S3, with almost all of the features, 
-all of the payoff of S4" - rstudio conf 2022, Hadley Wickham
-```
-
-* Compatible with S3: S7 objects are S3 objects!  Can even extend an S3 object with S7
-
-* Somewhat compatible with S4, see [compatability vignette](https://rconsortium.github.io/OOP-WG/articles/compatibility.html) for details. 
-
-* Helpful error messages! 
-
-* Note that it was previously called R7, but it was changed to "S7" to better reflect that it is functional not encapsulated! 
-
-## Abbreviated introduction based on the vignette {-}
-
-To install: 
-```{r, eval=FALSE}
-# install.packages("remotes")
-remotes::install_github("rconsortium/OOP-WG")
-```
-
-
-```{r, eval=FALSE}
-library(S7)
-dog <- new_class("dog", properties = list(
-  name = class_character,
-  age = class_numeric
-))
-dog
-
-
-#> <S7_class>
-#> @ name  :  dog
-#> @ parent: <S7_object>
-#> @ properties:
-#>  $ name: <character>          
-#>  $ age : <integer> or <double>
-```
-
-Note the 'class_character', these are S7 classes corresponding to the base classes.
-
-Now to use it:
-
-```{r, eval = FALSE}
-lola <- dog(name = "Lola", age = 11)
-lola
-
-#> <dog>
-#>  @ name: chr "Lola"
-#>  @ age : num 11
-```
-
-Properties can be set / read with '@', with automatic validation ('safety rails') based on the type!
-
-```{r, eval = FALSE}
-
-lola@age <- 12
-lola@age
-
-#> 12
-
-lola@age <- "twelve"
-
-#> Error: <dog>@age must be <integer> or <double>, not <character>
-
-```
-
-Note thehelpful error message!
-
-Like S3 (and S4) S7 has generics, implemented with `new_generic` and `method` for particular methods:
-
-```{r, eval = FALSE}
-speak <- new_generic("speak", "x")
-
-method(speak, dog) <- function(x) {
-  "Woof"
-}
-  
-speak(lola)
-
-#> [1] "Woof"
-```
-
-If we have another class, we can implement the generic for that too:
-
-```{r, eval = FALSE}
-cat <- new_class("cat", properties = list(
-  name = class_character,
-  age = class_double
-))
-method(speak, cat) <- function(x) {
-  "Meow"
-}
-
-fluffy <- cat(name = "Fluffy", age = 5)
-speak(fluffy)
-
-#> [1] "Meow"
-```
-
-Helpful messages:
-
-```{r, eval = FALSE}
-speak
-
-#> <S7_generic> speak(x, ...) with 2 methods:
-#> 1: method(speak, cat)
-#> 2: method(speak, dog)
-```
-
-
-"most usage of S7 with S3 will just work"
-
-```{r, eval = FALSE}
-method(print, cat) <- function(...) {
-  print("I am a cat.")
-}
-
-print(fluffy)
-#> "I am a cat"
-
-```
-
-*For validators, inheritance, dynamic properties and more,  see the [vignette!](https://rconsortium.github.io/OOP-WG/articles/S7.html)*
-
-https://rconsortium.github.io/OOP-WG/articles/S7.html
-
-## So... switch to S7 ? {-}
-
-$$
-\huge
-\textbf{Soon}^{tm}
-$$
-
-* Not yet... still in development! 
-
-* But consider trying it out:
-
-   * To stay ahead of the curve... S7 will be integrated into base R someday!
-   
-   * To contribute feedback to the S7 team!
-
-   * To get "almost all" of the benefits of S4 without the complexity !  
-   
-* In particular, if you have a new project that might require the complexity of S4, consider S7 instead!
-
-## Meeting Videos
-
-### Cohort 1
-
-`r knitr::include_url("https://www.youtube.com/embed/W1uc8HbyZvI")`
-
-### Cohort 2
-
-`r knitr::include_url("https://www.youtube.com/embed/bzo37PHCM1I")`
-
-### Cohort 3
-
-`r knitr::include_url("https://www.youtube.com/embed/_byYFTQHp1Y")`
-
-### Cohort 4
-
-`r knitr::include_url("https://www.youtube.com/embed/vdKDPBcOc6Y")`
-
-### Cohort 5
-
-`r knitr::include_url("https://www.youtube.com/embed/3EvqtVYTFVM")`
-
-### Cohort 6
-
-`r knitr::include_url("https://www.youtube.com/embed/vEButxFIvLw")`
-
-<details>
-<summary> Meeting chat log </summary>
-
-```
-00:11:36	Oluwafemi Oyedele:	I have not built anything with them!!!
-00:16:31	Arthur Shaw:	https://cran.r-project.org/web/packages/sp/index.html
-00:19:05	Arthur Shaw:	Apparently Hadley asked the same question we're asking several years ago: https://stackoverflow.com/questions/5437238/which-packages-make-good-use-of-s4-objects
-00:19:16	Trevin:	HA
-00:23:54	Trevin:	Your audio is breaking up Federica
-01:06:58	Federica Gazzelloni:	https://mastering-shiny.org/reactive-motivation.html?q=R6#event-driven
-01:07:37	Federica Gazzelloni:	https://engineering-shiny.org/common-app-caveats.html?q=R6#using-r6-as-data-storage
-01:10:52	Oluwafemi Oyedele:	Thank you !!!
-```
-</details>
-
-### Cohort 7
-
-`r knitr::include_url("https://www.youtube.com/embed/2vxnzqWp-OU")`
+# Trade-offs
+
+**Learning objectives:**
+
+- Understand the Trade-offs between S3, R6 and S4
+
+- Brief intro to S7 (the object system formerly known as R7)
+
+
+## Introduction {-}
+
+* We have three OOP systems introduced so far (S3, S4, R6) 
+
+* At the current time (pre - S7?) Hadley recommends use S3 by default: It's simple and widely used throughout base R and CRAN.
+
+* If you have experience in other languages,  *Resist* the temptation to use R6 even though it will feel more familiar!
+
+
+## S4 versus S3 {-}
+
+**Which functional object system to use, S3 or S4? **
+
+- **S3** is a simple and flexible system.
+   
+   - Good for small teams who need flexibility and immediate payoffs.
+   
+   - Commonly used throughout base R and CRAN 
+   
+   - Flexibility can cause problems, more complex systems might require formal conventions
+   
+
+- **S4** is a more formal, strict system. 
+
+   - Good for large projects and large teams
+   
+   - Used by Bioconductor project
+   
+   - Requires significant up front investment in design, but payoff is a robust system that enforces conventions.
+   
+   - S4 documentation is challenging to use. 
+    
+
+
+## R6 versus S3 {-}
+
+**R6** is built on **encapsulated objects**, rather than generic functions.   
+
+
+**Big differences: general trade-offs**
+
+* A generic is a regular function so it lives in the global namespace. An R6 method belongs to an object so it lives in a local namespace. This influences how we think about naming.
+
+* R6's reference semantics allow methods to simultaneously return a value and modify an object. This solves a painful problem called "threading state".
+
+* You invoke an R6 method using `$`, which is an infix operator. If you set up your methods correctly you can use chains of method calls as an alternative to the pipe.
+
+## Namespacing {-}
+
+**Where methods are found?**
+
+- in S3, **Generic functions** are **global** and live in the **global namespace**
+
+   - Advantage: Uniform API: `summary`, `print`, `predict` etc.
+   
+   - Disadvantage: Must be careful about creating new methods!  Homonyms must be avoided, don't define `plot(bank_heist)`
+ 
+
+- in R6, **Encapsulated methods** are **local**: objects with a **scope**
+
+   - Advantage: No problems with homonyms:  meaning of `bank_heist$plot()` is clear and unambiguous.
+   
+   - Disadvantage: Lack of a uniform API, except by convention.
+   
+
+## Threading state {-}
+
+
+In S3 the challenge is to return a value and modify the object. 
+
+
+```{r}
+new_stack <- function(items = list()) {
+  structure(list(items = items), class = "stack")
+}
+
+push <- function(x, y) {
+  x$items <- c(x$items, list(y))
+  x
+}
+```
+
+No problem with that, but what about when we want to pop a value?  We need to return two things.
+
+```{r}
+pop <- function(x) {
+  n <- length(x$items)
+  
+  item <- x$items[[n]]
+  x$items <- x$items[-n]
+  
+  list(item = item, x = x)
+}
+```
+
+The usage is a bit awkward:
+
+```{r}
+s <- new_stack()
+s <- push(s, 10)
+s <- push(s, 20)
+
+out <- pop(s)
+# Update state:
+s <- out$x
+
+print(out$item)
+```
+
+
+In python and other languages we have structured binding to make this less awkward.  R has the {zeallot} package. For more, see this vignette:
+
+```{r 16-Trade-offs-5, eval=FALSE}
+vignette('unpacking-assignment')
+```
+
+However, this is all easier in R6 due to the reference semantics!
+
+```{r}
+Stack <- R6::R6Class("Stack", list(
+  items = list(),
+  push = function(x) {
+    self$items <- c(self$items, x)
+    invisible(self)
+  },
+  pop = function() {
+    item <- self$items[[self$length()]]
+    self$items <- self$items[-self$length()]
+    item
+  },
+  length = function() {
+    length(self$items)
+  }
+))
+
+s <- Stack$new()
+s$push(10)
+s$push(20)
+s$pop()
+```
+
+
+## Method chaining {-}
+
+Useful to compose functions from left-to-right.
+
+Use of the operators:
+
+- S3: `|>` or `%>%`
+
+- R6: `$`
+
+```{r}
+s$push(44)$push(32)$pop()
+```
+
+
+## Umm... what about S7 ? {-}
+
+```{r standards, echo = FALSE,  fig.cap = "https://xkcd.com/927/"}
+
+knitr::include_graphics("https://imgs.xkcd.com/comics/standards_2x.png")
+
+```
+
+### Primary references: {-}
+
+* Docs: <https://rconsortium.github.io/S7/>
+
+* Talk by Hadley Wickham <https://www.youtube.com/watch?v=P3FxCvSueag>
+
+## S7 briefly {-}
+
+* S7 is a 'better' version of S3 with some of the 'strictness' of S4.
+
+```
+"A little bit more complex then S3, with almost all of the features, 
+all of the payoff of S4" - rstudio conf 2022, Hadley Wickham
+```
+* S3 + S4 = S7
+
+* Compatible with S3: S7 objects are S3 objects!  Can even extend an S3 object with S7
+
+* Somewhat compatible with S4, see [compatability vignette](https://rconsortium.github.io/S7/articles/compatibility.html) for details. 
+
+* Helpful error messages! 
+
+* Note that it was previously called R7, but it was changed to "S7" to better reflect that it is functional not encapsulated! 
+
+## Abbreviated introduction based on the vignette {-}
+
+To install (it's now on CRAN): 
+```{r, eval=FALSE}
+install.packages("S7")
+```
+
+
+```{r, eval=FALSE}
+library(S7)
+dog <- new_class("dog", properties = list(
+  name = class_character,
+  age = class_numeric
+))
+dog
+
+
+#> <S7_class>
+#> @ name  :  dog
+#> @ parent: <S7_object>
+#> @ properties:
+#>  $ name: <character>          
+#>  $ age : <integer> or <double>
+```
+
+Note the `class_character`, these are S7 classes corresponding to the base classes.
+
+Now to use it to create an object of class _dog_:
+
+```{r, eval = FALSE}
+lola <- dog(name = "Lola", age = 11)
+lola
+
+#> <dog>
+#>  @ name: chr "Lola"
+#>  @ age : num 11
+```
+
+Properties can be set/read with `@`, with automatic validation ('safety rails') based on the type!
+
+```{r, eval = FALSE}
+
+lola@age <- 12
+lola@age
+
+#> 12
+
+lola@age <- "twelve"
+
+#> Error: <dog>@age must be <integer> or <double>, not <character>
+
+```
+
+Note the helpful error message!
+
+Like S3 (and S4) S7 has generics, implemented with `new_generic` and `method` for particular methods:
+
+```{r, eval = FALSE}
+speak <- new_generic("speak", "x")
+
+method(speak, dog) <- function(x) {
+  "Woof"
+}
+  
+speak(lola)
+
+#> [1] "Woof"
+```
+
+If we have another class, we can implement the generic for that too:
+
+```{r, eval = FALSE}
+cat <- new_class("cat", properties = list(
+  name = class_character,
+  age = class_double
+))
+method(speak, cat) <- function(x) {
+  "Meow"
+}
+
+fluffy <- cat(name = "Fluffy", age = 5)
+speak(fluffy)
+
+#> [1] "Meow"
+```
+
+Helpful messages:
+
+```{r, eval = FALSE}
+speak
+
+#> <S7_generic> speak(x, ...) with 2 methods:
+#> 1: method(speak, cat)
+#> 2: method(speak, dog)
+```
+
+
+"most usage of S7 with S3 will just work"
+
+```{r, eval = FALSE}
+method(print, cat) <- function(...) {
+  print("I am a cat.")
+}
+
+print(fluffy)
+#> "I am a cat"
+
+```
+
+*For validators, inheritance, dynamic properties and more,  see the [vignette!](https://rconsortium.github.io/S7/articles/S7.html)*
+
+
+## So... switch to S7 ? {-}
+
+$$
+\huge
+\textbf{Soon}^{tm}
+$$
+
+* Not yet... still in development! ![Lifecycle: experimental](https://img.shields.io/badge/lifecycle-experimental-orange.svg)
+
+* But consider trying it out:
+
+   * To stay ahead of the curve... S7 will be integrated into base R someday!
+   
+   * To contribute feedback to the S7 team!
+
+   * To get "almost all" of the benefits of S4 without the complexity !  
+   
+* In particular, if you have a new project that might require the complexity of S4, consider S7 instead!
+
+## OOP system comparison {-}
+
+| Characteristic | S3 | S4 | S7 | R6 |
+|-------|------|------|------|------|
+| _Package_ | base R | base R  | [S7](https://rconsortium.github.io/S7/)  | [R6](https://r6.r-lib.org/)  |
+| _Programming type_ | Functional | Functional | Functional | Encapulated |
+| _Complexity_ | Low  | High  | Medium  | High  |
+| _Payoff_ | Low  | High  | High  | High  |
+| _Team size_ | Small | Small-large | Large  | ?  |
+| _Namespace_ | Global | Global?  | Global?  | Local  |
+| _Modify in place_ | No | No  | No  | Yes  |
+| _Method chaining_ | `|>` | `|>`?  | `|>`?  | `$`  |
+| _Get/set component_ | `$` | `@` | `@` | `$` |
+| _Create class_ | `class()` or `structure()` with `class` argument | `setClass()` | `new_class()` | `R6Class()` |
+| _Create validator_ | `function()` | `setValidity()` or `validator` argument in `setClass()` | `validator` argument in `new_class()` | `$validate()` |
+| _Create generic_ | `UseMethod()` | `setGeneric()` | `new_generic()` | NA |
+| _Create method_ | `function()` assigned to `generic.method` | `setMethod()` | `method()` | `R6Class()` |
+| _Create object_ | `class()` or `structure()` with `class` argument or constructor function | `new()` | Use registered method function | `$new()` |
+| _Additional components_ | attributes  | slots  | properties  |  |
+|  |  |  |  |  |
+
+## Meeting Videos {-}
+
+### Cohort 1 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/W1uc8HbyZvI")`
+
+### Cohort 2 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/bzo37PHCM1I")`
+
+### Cohort 3 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/_byYFTQHp1Y")`
+
+### Cohort 4 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/vdKDPBcOc6Y")`
+
+### Cohort 5 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/3EvqtVYTFVM")`
+
+### Cohort 6 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/vEButxFIvLw")`
+
+<details>
+<summary> Meeting chat log </summary>
+
+```
+00:11:36	Oluwafemi Oyedele:	I have not built anything with them!!!
+00:16:31	Arthur Shaw:	https://cran.r-project.org/web/packages/sp/index.html
+00:19:05	Arthur Shaw:	Apparently Hadley asked the same question we're asking several years ago: https://stackoverflow.com/questions/5437238/which-packages-make-good-use-of-s4-objects
+00:19:16	Trevin:	HA
+00:23:54	Trevin:	Your audio is breaking up Federica
+01:06:58	Federica Gazzelloni:	https://mastering-shiny.org/reactive-motivation.html?q=R6#event-driven
+01:07:37	Federica Gazzelloni:	https://engineering-shiny.org/common-app-caveats.html?q=R6#using-r6-as-data-storage
+01:10:52	Oluwafemi Oyedele:	Thank you !!!
+```
+</details>
+
+### Cohort 7 {-}
+
+`r knitr::include_url("https://www.youtube.com/embed/2vxnzqWp-OU")`