diff --git a/src/Highlight.php b/src/Highlight.php
index 771727f..2358094 100644
--- a/src/Highlight.php
+++ b/src/Highlight.php
@@ -4,7 +4,8 @@ namespace Kilo;
 
 class Highlight {
 	public const NORMAL = 0;
-	public const STRING = 1;
-	public const NUMBER = 2;
-	public const MATCH = 3;
+	public const COMMENT = 1;
+	public const STRING = 2;
+	public const NUMBER = 3;
+	public const MATCH = 4;
 }
\ No newline at end of file
diff --git a/src/Row.php b/src/Row.php
index eb2bbd2..09a33ec 100644
--- a/src/Row.php
+++ b/src/Row.php
@@ -114,6 +114,8 @@ class Row {
 	{
 		$this->hl = array_fill(0, $this->rsize, Highlight::NORMAL);
 
+		$scs = $this->parent->syntax->singleLineCommentStart;
+
 		$prevSep = TRUE;
 		$inString = '';
 
@@ -129,6 +131,14 @@ class Row {
 				return;
 			}
 
+			// Single-line comments
+			if ($scs !== '' && empty($inString) && substr($this->render, $i, strlen($scs)) === $scs)// strncmp($char, $scs, strlen($scs)) === 0)
+			{
+				array_replace_range($this->hl, $i, $this->rsize - $i, Highlight::COMMENT);
+				break;
+			}
+
+			// String/Char literals
 			if ($this->parent->syntax->flags & Syntax::HIGHLIGHT_STRINGS)
 			{
 				if ($inString !== '')
@@ -161,9 +171,9 @@ class Row {
 				}
 			}
 
+			// Numbers, including decimal points
 			if ($this->parent->syntax->flags & Syntax::HIGHLIGHT_NUMBERS)
 			{
-				// Numbers, including decimal points
 				if (
 					($char === '.' && $prevHl === Highlight::NUMBER) ||
 					(($prevSep || $prevHl === Highlight::NUMBER) && is_digit($char))
diff --git a/src/Syntax.php b/src/Syntax.php
index e7c31dd..7959916 100644
--- a/src/Syntax.php
+++ b/src/Syntax.php
@@ -8,14 +8,19 @@ class Syntax {
 
 	public string $filetype = '';
 	public array $filematch = [];
+	public string $singleLineCommentStart = '//';
+
 	public int $flags = 0;
 
-	public static function new(string $name, array $extList, int $flags): self
+	public static function new(string $name, array $extList, string $slcs, int $flags): self
 	{
 		$self = new self();
 
 		$self->filetype = $name;
 		$self->filematch = $extList;
+
+		$self->singleLineCommentStart = '//';
+
 		$self->flags = $flags;
 
 		return $self;
diff --git a/src/functions.php b/src/functions.php
index 9860583..3b4fae1 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -280,6 +280,9 @@ function syntax_to_color(int $hl): int
 {
 	switch ($hl)
 	{
+		case Highlight::COMMENT:
+			return 36; // Foreground Cyan
+
 		case Highlight::STRING:
 			return 35; // Foreground Magenta
 
diff --git a/src/hldb.php b/src/hldb.php
index f3305eb..8489bcc 100644
--- a/src/hldb.php
+++ b/src/hldb.php
@@ -12,26 +12,31 @@ function get_hldb(): array
 			Syntax::new(
 				'C',
 				['.c', '.h', '.cpp'],
+				'//',
 				Syntax::HIGHLIGHT_NUMBERS | Syntax::HIGHLIGHT_STRINGS,
 			),
 			Syntax::new(
 				'CSS',
 				['.css', '.less', '.sass', 'scss'],
+				'',
 				Syntax::HIGHLIGHT_NUMBERS | Syntax::HIGHLIGHT_STRINGS,
 			),
 			Syntax::new(
 				'JavaScript',
 				['.js', '.jsx', '.ts', '.tsx', '.jsm', '.es'],
+				'//',
 				Syntax::HIGHLIGHT_NUMBERS | Syntax::HIGHLIGHT_STRINGS,
 			),
 			Syntax::new(
 				'PHP',
 				['.php'],
+				'//',
 				Syntax::HIGHLIGHT_NUMBERS | Syntax::HIGHLIGHT_STRINGS,
 			),
 			Syntax::new(
 				'Rust',
 				['.rs'],
+				'//',
 				Syntax::HIGHLIGHT_NUMBERS | Syntax::HIGHLIGHT_STRINGS,
 			),
 		];