diff --git a/src/ludus/prelude.ld b/src/ludus/prelude.ld
index 5afd761..3a0bb72 100644
--- a/src/ludus/prelude.ld
+++ b/src/ludus/prelude.ld
@@ -136,7 +136,7 @@ fn empty? {
 	"Returns true if something is empty. Otherwise returns false (including for things that can't logically be empty, like numbers)."
 	([]) -> true
 	(#{}) -> true
-	(s as :set) -> eq (s, ${})
+	(s as :set) -> eq? (s, ${})
 	(()) -> true
 	("") -> true
 	(_) -> false
@@ -165,6 +165,8 @@ fn set? {
 	(_) -> false
 }
 
+& add a contains? or has? function
+
 fn fold {
 	"Folds a list."
 	(f as :fn, xs as :list) -> fold (f, xs, f ())
@@ -179,7 +181,7 @@ fn fold {
 }
 
 fn map {
-	"Maps over a list."
+	"Maps a function over a list: returns a new list with elements that are the result of applying the function to each element in the original list. E.g., `map ([1, 2, 3], inc) &=> [2, 3, 4]`."
 	(f as :fn, xs) -> {
 		fn mapper (prev, curr) -> append (prev, f (curr))
 		fold (mapper, xs, [])
@@ -191,7 +193,7 @@ fn map {
 }
 
 fn filter {
-	"Takes a list and a predicate function, and returns a new list with only the items that produce truthy values when the function is called on them."
+	"Takes a list and a predicate function, and returns a new list with only the items that produce truthy values when the function is called on them. E.g., `filter ([1, 2, 3, 4], odd?) &=> [1, 3]`."
 	(p? as :fn, xs) -> {
 		fn filterer (filtered, x) -> if p? (x)
 			then append (filtered, x)
@@ -375,7 +377,7 @@ fn mult {
 	() -> 1
 	(x as :number) -> x
 	(x as :number, y as :number) -> base :mult (x, y)
-	(x, y, ...zs) -> fold (base :mult, mult (x, y), zs)
+	(x, y, ...zs) -> fold (base :mult, zs, mult (x, y))
 	(scalar as :number, (x, y)) -> (mult (x, scalar), mult (y, scalar))
 	((x, y), scalar as :number) -> mult (scalar, (x, y))
 }
@@ -413,10 +415,20 @@ fn div/safe {
 	}
 }
 
+fn inv {
+	"Returns the inverse of a number: 1/n or `div (1, n)`. Panics on division by zero."
+	(x as :number) -> div (1, x)
+}
+
+fn inv/0 {
+	"Returns the inverse of a number: 1/n or `div/0 (1, n)`. Returns 0 on division by zero."
+	(x as :number) -> div/0 (1, x)
+}
+
 fn abs {
 	"Returns the absolute value of a number."
 	(0) -> 0
-	(n) -> if neg? (n) then mult (-1, n) else n
+	(n as :number) -> if neg? (n) then mult (-1, n) else n
 }
 
 fn neg {
@@ -483,6 +495,14 @@ fn lte? {
 	}
 }
 
+fn between? {
+	"Returns true if a number is in the range [lower, higher): greater than or equal to the lower number, less than the higher."
+	(lower as :number, higher as :number, x as :number) -> and (
+		gte? (x, lower)
+		lt? (x, higher)
+	)
+}
+
 fn neg? {
 	"Returns true if a value is a negative number, otherwise returns false."
 	(x as :number) if lt? (x, 0) -> true
@@ -497,16 +517,30 @@ fn pos? {
 
 fn even? {
 	"Returns true if a value is an even number, otherwise returns false."
-	(x as :number) if eq (0, mod (x, 2)) -> true
+	(x as :number) if eq? (0, mod (x, 2)) -> true
 	(_) -> false
 }
 
 fn odd? {
 	"Returns true if a value is an odd number, otherwise returns false."
-	(x as :number) if eq (1, mod (x, 2)) -> true
+	(x as :number) if eq? (1, mod (x, 2)) -> true
 	(_) -> false
 }
 
+fn min {
+	"Returns the number in its arguments that is closest to negative infinity."
+	(x as :number) -> x
+	(x as :number, y as :number) -> if lt? (x, y) then x else y
+	(x, y, ...zs) -> fold (min, zs, min (x, y)) 
+}
+
+fn max {
+	"Returns the number in its arguments that is closest to positive infinity."
+	(x as :number) -> x
+	(x as :number, y as :number) -> if gt? (x, y) then x else y
+	(x, y, ...zs) -> fold (max, zs, max (x, y))
+}
+
 &&& keywords: funny names
 fn keyword? {
 	"Returns true if a value is a keyword, otherwise returns false."
@@ -590,6 +624,7 @@ fn or {
 
 &&& associative collections: dicts, structs, namespaces
 & TODO?: get_in, update_in, merge
+& TODO?: consider renaming these: put & take, not assoc/dissoc
 fn assoc {
 	"Takes a dict, key, and value, and returns a new dict with the key set to value."
 	() -> #{}
@@ -677,6 +712,7 @@ fn assoc? {
 	(_) -> false
 }
 
+& TODO: consider merging `get` and `at`
 fn get {
 	"Takes a dict or struct, key, and optional default value; returns the value at key. If the value is not found, returns nil or the default value. Returns nil or default if the first argument is not a dict or struct."
 	(key as :keyword) -> get (key, _)
@@ -684,6 +720,7 @@ fn get {
 	(key as :keyword, coll, default) -> base :get (key, coll, default)
 }
 
+& TODO: add sets to this?
 fn has? {
 	"Takes a key and a dict, and returns true if there is a non-`nil` value stored at the key."
 	(key as :keyword) -> has? (key, _)
@@ -691,8 +728,7 @@ fn has? {
 }
 
 fn dict {
-	"Takes a struct or ns, and returns it as a dict. Or, takes a list or tuple of (key, value) tuples and returns it as a dict. Returns dicts unharmed."
-	(struct as :struct) -> base :to_dict (struct)
+	"Takes an ns, and returns it as a dict. Or, takes a list or tuple of (key, value) tuples and returns it as a dict. Returns dicts unharmed."
 	(ns_ as :ns) -> base :to_dict (ns_)
 	(dict as :dict) -> dict
 	(list as :list) -> fold (assoc, list)
@@ -829,12 +865,25 @@ fn dist {
 }
 
 &&& more number functions
-& TODO: add max, min
 fn random {
-	"Returns a random number. With zero arguments, returns a random number between 0 (inclusive) and 1 (exclusive). With one argument, returns a random number between 0 and n. With two arguments, returns a random number between m and n."
+	"Returns a random number. With zero arguments, returns a random number between 0 (inclusive) and 1 (exclusive). With one argument, returns a random number between 0 and n. With two arguments, returns a random number between m and n. Alternately, given a list, it returns a random member of that list."
 	() -> base :random ()
 	(n as :number) -> base :random (n)
 	(m as :number, n as :number) -> add (m, random (n))
+	(l as :list) -> {
+		let i = do l > count > random > floor
+		at (l, i)
+	}
+	(d as :dict) -> {
+		let key = do d > keys > random 
+		get (d, key)
+	}
+}
+
+fn random_int {
+	"Returns a random integer. With one argument, returns a random integer between 0 and that number. With two arguments, returns a random integer between them."
+	(n as :number) -> do n > random > floor
+	(m as :number, n as :number) -> floor (random (m, n))
 }
 
 fn floor {
@@ -853,7 +902,7 @@ fn round {
 }
 
 fn range {
-	"Returns the set of integers between start (inclusive) and end (exclusive) as a list. With one argument, starts at 0. If end is less than start, returns an empty list."
+	"Returns the set of integers between start (inclusive) and end (exclusive) as a list: [start, end). With one argument, starts at 0. If end is less than start, returns an empty list."
 	(end as :number) -> base :range (0, end)
 	(start as :number, end as :number) -> base :range (start, end)
 }
@@ -906,15 +955,25 @@ fn assert! {
 &&& Turtle & other graphics
 
 & some basic colors
-&&& TODO: add colors
+& these are the "basic" css colors
+& https://developer.mozilla.org/en-US/docs/Web/CSS/named-color
 let colors = #{
-	:white (255, 255, 255, 255)
-	:light_gray (150, 150, 150, 255)
-	:dark_gray (50, 50, 50, 255)
-	:red (255, 0, 0, 255)
-	:green (0, 255, 0, 255)
-	:blue (0, 0, 255, 255)
 	:black (0, 0, 0, 255)
+	:silver (192, 192, 192, 255)
+	:gray (128, 128, 128, 255)
+	:white (255, 255, 255, 255)
+	:maroon (128, 0, 0, 255)
+	:red (255, 0, 0, 255)
+	:purple (128, 0, 128, 255)
+	:fuchsia (255, 0, 255, 255)
+	:green (0, 128, 0, 255)
+	:lime (0, 255, 0, 255)
+	:olive (128, 128, 0, 255)
+	:yellow (255, 255, 0, 255)
+	:navy (0, 0, 128, 255)
+	:blue (0, 0, 255, 255)
+	:teal (0, 128, 128, 255)
+	:aqua (0, 255, 25, 255)
 }
 
 & the initial turtle state
@@ -986,6 +1045,7 @@ fn render_turtle! () -> {
 			add_call! ((:vertex, x2, y2))
 			add_call! ((:vertex, x3, y3))
 			add_call! ((:endShape))
+			& there's a happy bug here: the stroke will be the same width as the pen width. Keep this for now. Consider also showing the pen colour here?
 			add_call! ((:stroke, 0))
 			add_call! ((:line, 0, 0, x1, y1))
 			add_call! ((:pop))
@@ -1219,6 +1279,8 @@ ns prelude {
 	div
 	div/0
 	div/safe
+	inv
+	inv/0
 	angle
 	abs
 	neg
@@ -1231,6 +1293,9 @@ ns prelude {
 	gte?
 	lt?
 	lte?
+	min
+	max
+	between?
 	keyword?
 	nil?
 	some?
@@ -1269,6 +1334,7 @@ ns prelude {
 	sum_of_squares
 	dist
 	random
+	random_int
 	pi
 	tau
 	floor