diff --git a/DESCRIPTION b/DESCRIPTION
index 6047550..b53d71f 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -8,7 +8,7 @@ Description: Generate a palette of tints, shades or both from a single colour.
 URL: https://github.com/poissonconsulting/tinter
 BugReports: https://github.com/poissonconsulting/tinter/issues
 Imports: 
-    checkr,
+    chk,
     grDevices
 Suggests: 
     graphics,
diff --git a/NAMESPACE b/NAMESPACE
index c1d6355..06d81d3 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -3,4 +3,4 @@
 export(darken)
 export(lighten)
 export(tinter)
-import(checkr)
+import(chk)
diff --git a/R/namespace.R b/R/namespace.R
index cf772bd..33ffad1 100644
--- a/R/namespace.R
+++ b/R/namespace.R
@@ -1,2 +1,2 @@
-#' @import checkr
+#' @import chk
 NULL
diff --git a/R/tinter.R b/R/tinter.R
index 54686f9..2082fd4 100644
--- a/R/tinter.R
+++ b/R/tinter.R
@@ -14,13 +14,13 @@
 #' tinter("#fa6a5c", direction = "tints")
 
 tinter <- function(x, steps = 5, crop = 1, direction = "both", adjust = 0){
-
   check_colour(x)
-  check_length(x, length = 1L)
-  steps <- check_noneg_int(steps, coerce = TRUE)
-  crop <- check_noneg_int(crop, coerce = TRUE)
-  check_vector(direction, values = c("shades", "tints", "both"))
-  check_vector(adjust, c(-1, 1))
+  chk_whole_number(steps)
+  chk_whole_number(crop)
+  chk_string(direction)
+  chk_subset(direction, c("shades", "tints", "both"))
+  chk_number(adjust)
+  chk_range(adjust, c(-1, 1))
 
   if(crop > steps)
     stop("crop cannot be greater than steps.", call. = FALSE)
@@ -58,7 +58,8 @@ tinter <- function(x, steps = 5, crop = 1, direction = "both", adjust = 0){
 
 darken <- function(x, amount){
   lapply(x, check_colour)
-  check_vector(amount, values = c(0, 1))
+  chk_number(amount)
+  chk_range(amount)
   sapply(x, function(x){shade(x, 100, 0)[amount*100]}, USE.NAMES = FALSE)
 }
 
@@ -74,7 +75,8 @@ darken <- function(x, amount){
 
 lighten <- function(x, amount){
   lapply(x, check_colour)
-  check_vector(amount, values = c(0, 1))
+  chk_number(amount)
+  chk_range(amount)
 
   if(amount == 0){
     amount <- 0.01
diff --git a/R/utils.R b/R/utils.R
index 20806fb..ce65fc4 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -15,6 +15,7 @@ tint <- function(x, steps, crop){
 }
 
 check_colour <- function(x){
+  chk_string(x)
   res <- try(grDevices::col2rgb(x),silent = TRUE)
   if(class(res) == "try-error")
     stop(x, " is not a valid color", call. = FALSE)
diff --git a/README.Rmd b/README.Rmd
index 59e7fb6..28fa93d 100644
--- a/README.Rmd
+++ b/README.Rmd
@@ -149,22 +149,20 @@ grDevices::colorRampPalette(colors = c("white", "blue", "black"))(11)[-(c(1:2, 1
 
 ## Installation
 
-To install from CRAN
-```
+To install the latest release from [CRAN](https://cran.r-project.org)
+```{r, eval=FALSE}
 install.packages("tinter")
 ```
 
-To install the latest development version from [GitHub](https://github.com/poissonconsulting/tinter)
-```
-install.packages("devtools")
-devtools::install_github("poissonconsulting/err")
-devtools::install_github("poissonconsulting/checkr")
-devtools::install_github("poissonconsulting/tinter")
+To install the developmental version from [GitHub](https://github.com/poissonconsulting/tinter)
+```{r, eval=FALSE}
+# install.packages("remotes")
+remotes::install_github("poissonconsulting/tinter")
 ```
 
-To install the latest development version from the Poisson drat [repository](https://github.com/poissonconsulting/drat)
-```
-install.packages("drat")
+To install the latest developmental release from the Poisson drat [repository](https://github.com/poissonconsulting/drat)
+```{r, eval=FALSE}
+# install.packages("drat")
 drat::addRepo("poissonconsulting")
 install.packages("tinter")
 ```
diff --git a/README.md b/README.md
index cff8b9a..36a7976 100644
--- a/README.md
+++ b/README.md
@@ -125,24 +125,28 @@ grDevices::colorRampPalette(colors = c("white", "blue", "black"))(11)[-(c(1:2, 1
 
 ## Installation
 
-To install from CRAN
+To install the latest release from [CRAN](https://cran.r-project.org)
 
-    install.packages("tinter")
+``` r
+install.packages("tinter")
+```
 
-To install the latest development version from
+To install the developmental version from
 [GitHub](https://github.com/poissonconsulting/tinter)
 
-    install.packages("devtools")
-    devtools::install_github("poissonconsulting/err")
-    devtools::install_github("poissonconsulting/checkr")
-    devtools::install_github("poissonconsulting/tinter")
+``` r
+# install.packages("remotes")
+remotes::install_github("poissonconsulting/tinter")
+```
 
-To install the latest development version from the Poisson drat
+To install the latest developmental release from the Poisson drat
 [repository](https://github.com/poissonconsulting/drat)
 
-    install.packages("drat")
-    drat::addRepo("poissonconsulting")
-    install.packages("tinter")
+``` r
+# install.packages("drat")
+drat::addRepo("poissonconsulting")
+install.packages("tinter")
+```
 
 ## Contribution