diff --git a/.ameba.yml b/.ameba.yml
index 812b3b2..b567470 100644
--- a/.ameba.yml
+++ b/.ameba.yml
@@ -14,14 +14,9 @@ Naming/QueryBoolMethods:
 Naming/BlockParameterName:
   Enabled: false
 
-Style/UnlessElse:
-  Enabled: false
-
 Style/ParenthesesAroundCondition:
-  Enabled: false
-
-Style/NegatedConditionsInUnless:
-  Enabled: false
+  Enabled: true
+  AllowSafeAssignment: true
 
 Lint/NotNil:
   Excluded:
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index 6a883a4..8cd47f4 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -78,11 +78,11 @@ def extract_spec_tests(file)
   result_start = false
 
   begin
-    File.open(file) do |f|
+    File.open(file) do |input|
       line_number = 0
       test_tags = ""
 
-      while line = f.read_line
+      while (line = input.read_line)
         line_number += 1
         line = line.gsub(/\r\n?/, "\n")
         break if line.includes?("<!-- END TESTS -->")
diff --git a/src/markd/html_entities.cr b/src/markd/html_entities.cr
index e5ae646..b383ad1 100644
--- a/src/markd/html_entities.cr
+++ b/src/markd/html_entities.cr
@@ -37,7 +37,7 @@ module Markd::HTMLEntities
         end
       else
         entities_key = chars[0..-1]
-        if resolved_entity = Markd::HTMLEntities::ENTITIES_MAPPINGS[entities_key]?
+        if (resolved_entity = Markd::HTMLEntities::ENTITIES_MAPPINGS[entities_key]?)
           return resolved_entity
         end
       end
@@ -48,7 +48,7 @@ module Markd::HTMLEntities
     def self.decode_codepoint(codepoint)
       return "\uFFFD" if codepoint >= 0xD800 && codepoint <= 0xDFFF || codepoint > 0x10FFF
 
-      if decoded = Markd::HTMLEntities::DECODE_MAPPINGS[codepoint]?
+      if (decoded = Markd::HTMLEntities::DECODE_MAPPINGS[codepoint]?)
         codepoint = decoded
       end
 
diff --git a/src/markd/node.cr b/src/markd/node.cr
index 09d2cdd..31223b3 100644
--- a/src/markd/node.cr
+++ b/src/markd/node.cr
@@ -84,7 +84,7 @@ module Markd
       child.unlink
       child.parent = self
 
-      if last = last_child?
+      if (last = last_child?)
         last.next = child
         child.prev = last
         @last_child = child
@@ -97,9 +97,9 @@ module Markd
     def insert_after(sibling : Node)
       sibling.unlink
 
-      if nxt = next?
+      if (nxt = next?)
         nxt.prev = sibling
-      elsif parent = parent?
+      elsif (parent = parent?)
         parent.last_child = sibling
       end
       sibling.next = nxt
@@ -110,15 +110,15 @@ module Markd
     end
 
     def unlink
-      if prev = prev?
+      if (prev = prev?)
         prev.next = next?
-      elsif parent = parent?
+      elsif (parent = parent?)
         parent.first_child = next?
       end
 
-      if nxt = next?
+      if (nxt = next?)
         nxt.prev = prev?
-      elsif parent = parent?
+      elsif (parent = parent?)
         parent.last_child = prev?
       end
 
@@ -158,7 +158,7 @@ module Markd
         entering = @entering
 
         if entering && current.type.container?
-          if first_child = current.first_child?
+          if (first_child = current.first_child?)
             @current = first_child
             @entering = true
           else
diff --git a/src/markd/parsers/block.cr b/src/markd/parsers/block.cr
index 60a467b..89a2597 100644
--- a/src/markd/parsers/block.cr
+++ b/src/markd/parsers/block.cr
@@ -76,7 +76,7 @@ module Markd::Parser
       # ignore last blank line created by final newline
       lines_size -= 1 if source.ends_with?('\n')
 
-      while tip = tip?
+      while (tip = tip?)
         token(tip, lines_size)
       end
     end
@@ -177,7 +177,7 @@ module Markd::Parser
           add_line
 
           # if HtmlBlock, check for end condition
-          if (container_type.html_block? && match_html_block?(container))
+          if container_type.html_block? && match_html_block?(container)
             token(container, @current_line)
           end
         elsif @offset < line.size && !@blank
@@ -269,7 +269,7 @@ module Markd::Parser
       if @line.empty?
         @blank = true
       else
-        while char = @line[offset]?
+        while (char = @line[offset]?)
           case char
           when ' '
             offset += 1
@@ -330,7 +330,7 @@ module Markd::Parser
     end
 
     private def match_html_block?(container : Node)
-      if block_type = container.data["html_block_type"]
+      if (block_type = container.data["html_block_type"])
         block_type = block_type.as(Int32)
         block_type >= 0 && block_type <= 4 && Rule::HTML_BLOCK_CLOSE[block_type].match(@line[@offset..-1])
       else
diff --git a/src/markd/parsers/inline.cr b/src/markd/parsers/inline.cr
index 49815de..74e537f 100644
--- a/src/markd/parsers/inline.cr
+++ b/src/markd/parsers/inline.cr
@@ -177,7 +177,7 @@ module Markd::Parser
 
       num_ticks = @pos - start_pos
       after_open_ticks = @pos
-      while text = match(Rule::TICKS)
+      while (text = match(Rule::TICKS))
         if text.bytesize == num_ticks
           child = Node.new(Node::Type::Code)
           child_text = @text.byte_slice(after_open_ticks, (@pos - num_ticks) - after_open_ticks).gsub(Rule::LINE_ENDING, " ")
@@ -387,9 +387,7 @@ module Markd::Parser
           case closer_char
           when '*', '_', '~'
             if closer_char != '~' || (closer_char == '~' && @options.gfm)
-              unless opener
-                closer = closer.next?
-              else
+              if opener
                 # calculate actual number of delimiters used from closer
                 use_delims = (closer.num_delims >= 2 && opener.num_delims >= 2) ? 2 : 1
 
@@ -444,6 +442,8 @@ module Markd::Parser
                   remove_delimiter(closer)
                   closer = tmp_stack
                 end
+              else
+                closer = closer.next?
               end
             end
           when '\''
@@ -476,17 +476,17 @@ module Markd::Parser
     end
 
     private def auto_link(node : Node)
-      if matched_text = match(Rule::EMAIL_AUTO_LINK)
+      if (matched_text = match(Rule::EMAIL_AUTO_LINK))
         node.append_child(link(matched_text, true))
         return true
-      elsif matched_text = match(Rule::AUTO_LINK)
+      elsif (matched_text = match(Rule::AUTO_LINK))
         node.append_child(link(matched_text, false))
         return true
       elsif @options.gfm && @options.autolink
         # These are all the extended autolinks from the
         # autolink extension
 
-        if matched_text = match(Rule::WWW_AUTO_LINK)
+        if (matched_text = match(Rule::WWW_AUTO_LINK))
           clean_text = autolink_cleanup(matched_text)
           if clean_text.empty?
             node.append_child(text(matched_text))
@@ -496,11 +496,11 @@ module Markd::Parser
             node.append_child(text(post)) if post.size > 0 && matched_text != clean_text
           end
           return true
-        elsif matched_text = (
+        elsif (matched_text = (
                 match(Rule::PROTOCOL_AUTO_LINK) ||
                 match(Rule::XMPP_AUTO_LINK) ||
                 match(Rule::MAILTO_AUTO_LINK)
-              )
+              ))
           clean_text = autolink_cleanup(matched_text)
           if clean_text.empty?
             node.append_child(text(matched_text))
@@ -510,7 +510,7 @@ module Markd::Parser
             node.append_child(text(post)) if post.size > 0 && matched_text != clean_text
           end
           return true
-        elsif matched_text = match(Rule::EXTENDED_EMAIL_AUTO_LINK)
+        elsif (matched_text = match(Rule::EXTENDED_EMAIL_AUTO_LINK))
           # Emails that end in - or _ are declared not to be links by the spec:
           #
           # `.`, `-`, and `_` can occur on both sides of the `@`, but only `.` may occur at
@@ -532,7 +532,7 @@ module Markd::Parser
     end
 
     private def html_tag(node : Node)
-      if text = match(Rule::HTML_TAG)
+      if (text = match(Rule::HTML_TAG))
         child = Node.new(Node::Type::HTMLInline)
 
         if @options.gfm && @options.tagfilter
@@ -614,7 +614,7 @@ module Markd::Parser
     end
 
     private def string(node : Node)
-      if text = match_main
+      if (text = match_main)
         if @options.smart?
           text = text.gsub(Rule::ELLIPSIS, '\u{2026}')
             .gsub(Rule::DASH) do |chars|
@@ -674,12 +674,12 @@ module Markd::Parser
     end
 
     private def link_destination
-      dest = if text = match(Rule::LINK_DESTINATION_BRACES)
+      dest = if (text = match(Rule::LINK_DESTINATION_BRACES))
                text[1..-2]
              elsif char_at?(@pos) != '<'
                save_pos = @pos
                open_parens = 0
-               while char = char_at?(@pos)
+               while (char = char_at?(@pos))
                  case char
                  when '\\'
                    @pos += 1
@@ -726,7 +726,7 @@ module Markd::Parser
 
       delimiter = Delimiter.new(char, num_delims, num_delims, child, @delimiters, nil, res[:can_open], res[:can_close])
 
-      if prev = delimiter.previous?
+      if (prev = delimiter.previous?)
         prev.next = delimiter
       end
 
@@ -736,11 +736,11 @@ module Markd::Parser
     end
 
     private def remove_delimiter(delimiter : Delimiter)
-      if prev = delimiter.previous?
+      if (prev = delimiter.previous?)
         prev.next = delimiter.next?
       end
 
-      if nxt = delimiter.next?
+      if (nxt = delimiter.next?)
         nxt.previous = delimiter.previous?
       else
         # top of stack
@@ -897,7 +897,7 @@ module Markd::Parser
     # Parse zero or more space characters, including at most one newline
     private def spnl
       seen_newline = false
-      while c = char_at?(@pos)
+      while (c = char_at?(@pos))
         if !seen_newline && c == '\n'
           seen_newline = true
         elsif c != ' '
@@ -912,7 +912,7 @@ module Markd::Parser
 
     private def match(regex : Regex) : String?
       text = @text.byte_slice(@pos)
-      if match = text.match(regex)
+      if (match = text.match(regex))
         @pos += match.byte_end.not_nil!
         return match[0]
       end
@@ -926,7 +926,7 @@ module Markd::Parser
 
     private def match_main : String?
       start_pos = @pos
-      while char = char_at?(@pos)
+      while (char = char_at?(@pos))
         # If we detected a special string (like a URL), and it's
         # not the beggining of the string, we need to break right away.
         #
diff --git a/src/markd/renderer.cr b/src/markd/renderer.cr
index c8d3d1e..e4bd30f 100644
--- a/src/markd/renderer.cr
+++ b/src/markd/renderer.cr
@@ -75,7 +75,7 @@ module Markd
     def render(document : Node, formatter : T?) forall T
       Utils.timer("rendering", @options.time) do
         walker = document.walker
-        while event = walker.next
+        while (event = walker.next)
           node, entering = event
 
           case node.type
diff --git a/src/markd/renderers/html_renderer.cr b/src/markd/renderers/html_renderer.cr
index a7df9fc..d7f2705 100644
--- a/src/markd/renderers/html_renderer.cr
+++ b/src/markd/renderers/html_renderer.cr
@@ -283,7 +283,7 @@ module Markd
     def strong(node : Node, entering : Bool) : Nil
       @strong_stack -= 1 if @options.gfm && !entering
 
-      tag("strong", end_tag: !entering) if (@strong_stack == 0)
+      tag("strong", end_tag: !entering) if @strong_stack == 0
 
       @strong_stack += 1 if @options.gfm && entering
     end
diff --git a/src/markd/rules/heading.cr b/src/markd/rules/heading.cr
index 4c304dc..23c1db1 100644
--- a/src/markd/rules/heading.cr
+++ b/src/markd/rules/heading.cr
@@ -6,7 +6,7 @@ module Markd::Rule
     SETEXT_HEADING_MARKER = /^(?:=+|-+)[ \t]*$/
 
     def match(parser : Parser, container : Node) : MatchValue
-      if match = match?(parser, ATX_HEADING_MARKER)
+      if (match = match?(parser, ATX_HEADING_MARKER))
         # ATX Heading matched
         parser.advance_next_nonspace
         parser.advance_offset(match[0].size, false)
diff --git a/src/markd/rules/html_block.cr b/src/markd/rules/html_block.cr
index c3df5ae..60d73bd 100644
--- a/src/markd/rules/html_block.cr
+++ b/src/markd/rules/html_block.cr
@@ -8,8 +8,8 @@ module Markd::Rule
         block_type_size = Rule::HTML_BLOCK_OPEN.size - 1
 
         Rule::HTML_BLOCK_OPEN.each_with_index do |regex, index|
-          if (text.match(regex) &&
-             (index < block_type_size || !container.type.paragraph?))
+          if text.match(regex) &&
+             (index < block_type_size || !container.type.paragraph?)
             parser.close_unmatched_blocks
             # We don't adjust parser.offset;
             # spaces are part of the HTML block:
@@ -47,18 +47,18 @@ module Markd::Rule
     end
 
     def self.escape_disallowed_html(text : String) : String
-      String.build do |s|
+      String.build do |string|
         pos = 0
 
         text.scan(/<\/?\s*(#{GFM_DISALLOWED_HTML_TAGS.join('|')})\b/i) do |match|
           start = text.index(match[0], pos)
           next if start.nil?
 
-          s << text[pos...start] << "&lt;#{match[0][1..]}"
+          string << text[pos...start] << "&lt;#{match[0][1..]}"
           pos = start + match[0].size
         end
 
-        s << text[pos..-1]
+        string << text[pos..-1]
       end
     end
   end
diff --git a/src/markd/rules/list.cr b/src/markd/rules/list.cr
index 73bc764..5f45639 100644
--- a/src/markd/rules/list.cr
+++ b/src/markd/rules/list.cr
@@ -6,9 +6,9 @@ module Markd::Rule
     ORDERED_LIST_MARKERS = {'.', ')'}
 
     def match(parser : Parser, container : Node) : MatchValue
-      if (!parser.indented || container.type.list?)
+      if !parser.indented || container.type.list?
         data = parse_list_marker(parser, container)
-        return MatchValue::None unless data && !data.empty?
+        return MatchValue::None if !data || data.empty?
 
         parser.close_unmatched_blocks
         if !parser.tip.type.list? || !list_match?(container.data, data)
@@ -167,7 +167,7 @@ module Markd::Rule
       while container
         return true if container.last_line_blank?
 
-        break unless !container.last_line_checked? && container.type.in?(Node::Type::List, Node::Type::Item)
+        break if container.last_line_checked? || !container.type.in?(Node::Type::List, Node::Type::Item)
         container.last_line_checked = true
         container = container.last_child?
       end
diff --git a/src/markd/rules/table.cr b/src/markd/rules/table.cr
index cda107c..af35c70 100644
--- a/src/markd/rules/table.cr
+++ b/src/markd/rules/table.cr
@@ -37,8 +37,8 @@ module Markd::Rule
     def token(parser : Parser, container : Node) : Nil
       lines = container.text.strip.split("\n")
 
-      row_sizes = lines[...2].map do |l|
-        strip_pipe(l.strip).split(TABLE_CELL_SEPARATOR).size
+      row_sizes = lines[...2].map do |line|
+        strip_pipe(line.strip).split(TABLE_CELL_SEPARATOR).size
       end.uniq!
 
       # Do we have a real table?