diff --git a/combinations.rb b/combinations.rb
new file mode 100644
index 0000000..52a5a44
--- /dev/null
+++ b/combinations.rb
@@ -0,0 +1,31 @@
+def combinations(arr1, arr2) 
+
+	# return if any array is empty
+	if arr1.length == 0 or arr2.length == 0
+		return arr1.length == 0 ? (arr2) : (arr1)
+	end
+
+	# initialize
+	combined_array = []
+
+	# combine arrays
+	arr1.each do |val1|
+		arr2.each do |val2|
+			combined_array << val1 + val2
+		end
+	end
+
+	return combined_array
+
+end
+
+# tests
+puts combinations(["on","in"],["to","rope"])
+puts "---------------"
+puts combinations(["a "], ["burrito", "coffee", "computer", "mouse", "rhino"])
+puts "---------------"
+puts combinations(["a", "b", "c", "d", "e"], ["1", "2", "3", "4", "5", "6", "7", "8", "9"])
+puts "---------------"
+puts combinations([],["1","a"])
+puts "---------------"
+puts combinations([],[])
\ No newline at end of file
diff --git a/counting_game.rb b/counting_game.rb
new file mode 100644
index 0000000..dbbf971
--- /dev/null
+++ b/counting_game.rb
@@ -0,0 +1,36 @@
+def counting_game(num_friends, count)
+
+	friend = 1
+	number = 1
+	direction = 1 # 1 or -1 depending on direction of friends counting
+
+	while number <= count
+
+		puts "Friend " + friend.to_s + " said " + number.to_s # statement
+
+		if number % 11 == 0 # important that this precedes friend change & number change
+			friend += direction
+		end
+
+		friend += direction # friend change
+
+		if friend > num_friends # back to first friend
+			friend -= num_friends
+		end
+		if friend <= 0 # back to last friend
+			friend += num_friends 
+		end
+
+		number += 1 # number change
+
+		if number % 7 == 0 # important that this comes after friend change & number change
+			direction *= -1
+		end
+
+	end
+
+end
+
+# tests
+counting_game(10, 100)
+# counting_game(6,200)
diff --git a/factorial.rb b/factorial.rb
new file mode 100644
index 0000000..b036f2c
--- /dev/null
+++ b/factorial.rb
@@ -0,0 +1,26 @@
+def factorial(num)
+
+	if num < 0 
+		return "out of scope for this method" 
+	elsif num < 2 
+		return 1
+	else
+		return num*factorial(num-1) # recursion
+	end
+
+end
+
+# tests 
+puts factorial(5)
+puts "---------------"
+puts factorial(0)
+puts "---------------"
+puts factorial(1)
+puts "---------------"
+puts factorial(2)
+puts "---------------"
+puts factorial(9)
+puts "---------------"
+puts factorial(12)
+puts "---------------"
+puts factorial(-1)
\ No newline at end of file
diff --git a/power.rb b/power.rb
new file mode 100644
index 0000000..a7471b3
--- /dev/null
+++ b/power.rb
@@ -0,0 +1,31 @@
+def power(base,exp)
+	
+	# immediately return if exp = 0
+	if exp == 0
+		return 1
+	end
+
+	# initialize
+	result = 1
+
+	# iterate to find result
+	exp.abs.times do 
+		result *= base
+	end
+
+	# return based on whether exp is pos or neg
+	return exp < 0 ? (1.0/result) : (result)
+
+end
+
+# tests
+puts power(1,3) 
+puts "---------------"
+puts power(8,10)
+puts "---------------"
+puts power(2,-2)
+puts "---------------"
+puts power(10,-5)
+puts "---------------"
+puts power(1000000000000000000000000,0)
+
diff --git a/prime.rb b/prime.rb
new file mode 100644
index 0000000..7d85989
--- /dev/null
+++ b/prime.rb
@@ -0,0 +1,32 @@
+def is_prime?(num)
+
+	# any number less than or equal to 1 is not prime
+	if num <= 1 
+		return false
+	end
+
+	(2..num/2).to_a.each do |i|
+		if num % i == 0
+			return false 
+		end
+	end
+
+	return true
+
+end
+
+# tests
+puts is_prime?(7) 
+puts "---------------"
+puts is_prime?(14)
+puts "---------------"
+puts is_prime?(-1)
+puts "---------------"
+puts is_prime?(0)
+puts "---------------"
+puts is_prime?(1)
+puts "---------------"
+puts is_prime?(2)
+puts "---------------"
+puts is_prime?(5)
+
diff --git a/rect_overlap.rb b/rect_overlap.rb
new file mode 100644
index 0000000..40d659f
--- /dev/null
+++ b/rect_overlap.rb
@@ -0,0 +1,47 @@
+
+def overlap(rect1, rect2) 
+
+	# assumptions
+	# the bottom-left and top-right corners are always given, rather than the bottom-right and top-left
+	# the coordinates for each rectangle are given as [bottom-left, top-right] or [top-right, bottom-left]
+	# the first rectangle given isn't always the most bottom and/or most left
+
+	# define corners of each rectange (bl = bottom-left, tr = top-right)
+	rect1_bl = rect1[0][0] < rect1[1][0] ? rect1[0] : rect1[1]
+	rect1_tr = rect1[0][0] > rect1[1][0] ? rect1[0] : rect1[1]
+	rect2_bl = rect2[0][0] < rect2[1][0] ? rect2[0] : rect2[1]
+	rect2_tr = rect2[0][0] > rect2[1][0] ? rect2[0] : rect2[1]
+
+	# make sure that rect1 is the most "bottom-left" & (crudely) swap if that is not the case
+	if rect1_bl[0] > rect2_bl[0] or rect1_bl[1] > rect2_bl[1] 
+		temp = rect1_bl
+		rect1_bl = rect2_bl
+		rect2_bl = temp
+		temp = rect1_tr
+		rect1_tr = rect2_tr
+		rect2_tr = temp
+	end
+
+	# print rectangles to check if swap (if necessary) worked
+	# puts '[' + rect1_bl[0].to_s + ',' + rect1_bl[1].to_s + '], ['  + rect1_tr[0].to_s + ',' + rect1_tr[1].to_s + ']'
+	# puts '[' + rect2_bl[0].to_s + ',' + rect2_bl[1].to_s + '], ['  + rect2_tr[0].to_s + ',' + rect2_tr[1].to_s + ']'
+
+	# check if rects overlap by comparing rect1_tr and rect2_bl
+	return rect2_bl[0] < rect1_tr[0] && rect2_bl[1] < rect1_tr[1]
+
+end
+
+puts overlap( [ [0,0],[3,3] ], [ [1,1],[4,5] ] ) # scenario 1, true
+puts "---------------"
+puts overlap( [ [0,0],[1,4] ], [ [1,1],[3,2] ] ) # scenario 2, false
+puts "---------------"
+puts overlap( [ [3,3],[0,0] ], [ [1,1],[4,5] ] ) # scenario 1, coords of rect1 swapped, true
+puts "---------------"
+puts overlap( [ [0,0],[1,4] ], [ [3,2],[1,1] ] ) # scenario 2, coords of rect2 swapped, false
+puts "---------------"
+puts overlap( [ [1,1],[4,5] ], [ [0,0],[3,3] ] ) # scenario 1, rect1 & rect2 swapped, true
+puts "---------------"
+puts overlap( [ [0,4],[5,5] ], [ [0,0],[4,4] ] ) # scenario 3, edge case, false
+
+
+
diff --git a/uniques.rb b/uniques.rb
new file mode 100644
index 0000000..007670d
--- /dev/null
+++ b/uniques.rb
@@ -0,0 +1,28 @@
+def uniques(arr) 
+
+	# initialize
+	no_dupes = []
+
+	# remove duplicates by iteration and checking preceding elements
+	arr.each_with_index do |val_outer, ind|
+		has_preceding_dupe = false 
+		arr[0...ind].each do |val_inner| # hinges on use of "..." (last val exclusive) NOT ".." (last val inclusive)
+			if val_outer == val_inner 
+				has_preceding_dupe = true
+			end
+		end
+		if not has_preceding_dupe
+			no_dupes << val_outer
+		end
+	end
+
+	return no_dupes
+
+end
+
+# tests
+puts uniques([1,5,"frog", 2,1,3,"frog"])
+puts "---------------"
+puts uniques([1,2,3,2,3,5,7,1,4,20,6,1,2])
+puts "---------------"
+puts uniques(["a", "A", "eh", "a", "eyy", "eyyy", "eyy"])
\ No newline at end of file