diff --git a/combinations.rb b/combinations.rb
new file mode 100644
index 0000000..e17daeb
--- /dev/null
+++ b/combinations.rb
@@ -0,0 +1,11 @@
+def combinations(a, b)
+  combos = []
+  a.each do |a_item|
+    b.each do |b_item|
+      combos << a_item + b_item
+    end
+  end
+  combos
+end
+
+combinations(["on", "in"], ["to", "rope"])
\ No newline at end of file
diff --git a/counting.rb b/counting.rb
new file mode 100644
index 0000000..19463b9
--- /dev/null
+++ b/counting.rb
@@ -0,0 +1,24 @@
+def counting(player_num, count_limit)
+  count = 1
+  players = []
+  player_id = 1
+  direction = 1
+ 
+  while count <= count_limit
+  	increment = 1
+  	# if count is divisible by 7, switch the direction
+  	if count % 7 == 0
+      direction *= -1
+  	# if count is divisible by 11, skip the next person
+  	end
+  	if count % 11 == 0
+  		increment = 2 
+  	end
+    puts "player#{player_id} says #{count}"
+    count += 1
+    player_id = (player_id + increment * direction) % player_num
+  end
+
+end
+
+counting(10, 100)
\ No newline at end of file
diff --git a/factorial.rb b/factorial.rb
new file mode 100644
index 0000000..30fc44e
--- /dev/null
+++ b/factorial.rb
@@ -0,0 +1,7 @@
+def factorial(num)
+  tmp = 1
+  1.upto(num) do |i|
+    tmp = tmp * i
+  end
+  tmp
+end
diff --git a/overlap.rb b/overlap.rb
new file mode 100644
index 0000000..1dfb1ee
--- /dev/null
+++ b/overlap.rb
@@ -0,0 +1,15 @@
+# NOTE: this function assumes that the two coordinates provided for each rectangle are left-bottom and right-top, in that order.
+def overlap(a, b)
+  # if x coordinates overlap
+   if (b[0][0] < a[1][0] && b[0][0] > a[0][0]) || (b[1][0] < a[1][0] && b[1][0] > a[0][0]) 
+    # check if y coordinates overlap
+    if (b[0][1] < a[1][1] && b[0][1] > a[0][1]) || (b[1][1] < a[1][1] && b[1][1] > a[0][1]) 
+      return true
+    end
+  end
+    return false
+
+end
+
+overlap( [ [0,0],[3,3] ], [ [1,1],[4,5] ] )
+overlap( [ [0,0],[1,4] ], [ [1,1],[3,2] ] )
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diff --git a/power.rb b/power.rb
new file mode 100644
index 0000000..7d3d199
--- /dev/null
+++ b/power.rb
@@ -0,0 +1,14 @@
+# Write a method power which takes two integers (base and exponent) and returns the base raised to the power of exponent. Do not use Ruby’s ** operator for this!
+
+# > power(3,4)
+# => 81 # (3*3*3*3)
+
+def power(base, exponent)
+  val = 1
+  exponent.times do 
+   val = val * base
+  end
+  val
+end
+
+puts power(3,4)
\ No newline at end of file
diff --git a/primes.rb b/primes.rb
new file mode 100644
index 0000000..d9efd19
--- /dev/null
+++ b/primes.rb
@@ -0,0 +1,14 @@
+def is_prime?(num)
+  i = 1
+  factors = []
+  while i <= num
+    if num % i == 0
+      factors << i
+    end
+    i += 1
+  end
+  if factors.length > 2 
+    return false
+  end
+  return true
+end
diff --git a/uniques.rb b/uniques.rb
new file mode 100644
index 0000000..9f3b1fe
--- /dev/null
+++ b/uniques.rb
@@ -0,0 +1,12 @@
+def uniques(array)
+  no_duplicates = []
+  array.each do |item|
+    unless no_duplicates.include? item
+      no_duplicates << item
+    end
+  end
+  no_duplicates
+
+end
+
+uniques([1,5,"frog", 2,1,3,"frog"])
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