diff --git a/bin/algs4.php b/bin/algs4.php
index 69f2aa9..4b93c70 100755
--- a/bin/algs4.php
+++ b/bin/algs4.php
@@ -14,5 +14,6 @@
     new Commands\AllowList(),
     new Commands\Average(),
     new Commands\RandomSeq(),
+    new Commands\Interval2D(),
 ]);
 $app->run();
\ No newline at end of file
diff --git a/src/Commands/Interval2D.php b/src/Commands/Interval2D.php
new file mode 100644
index 0000000..fff590a
--- /dev/null
+++ b/src/Commands/Interval2D.php
@@ -0,0 +1,92 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kellegous\Algs4\Commands;
+
+use Kellegous\Algs4\Counter;
+use Kellegous\Algs4\Interval1D;
+use Kellegous\Algs4\Point2D;
+use Kellegous\Algs4\Random;
+use Kellegous\Algs4\Stdio;
+use Override;
+use Random\Engine\Mt19937;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+use function Kellegous\Algs4\parse_float;
+use function Kellegous\Algs4\parse_int;
+
+#[AsCommand(
+    name: 'interval2d',
+    description: 'command associated with Interval2D'
+)]
+final class Interval2D extends Command
+{
+
+    #[Override]
+    protected function configure(): void
+    {
+        $this->addArgument(
+            'xmin',
+            InputArgument::REQUIRED,
+            'the minimum x coordinate'
+        );
+        $this->addArgument(
+            'xmax',
+            InputArgument::REQUIRED,
+            'the maximum x coordinate'
+        );
+        $this->addArgument(
+            'ymin',
+            InputArgument::REQUIRED,
+            'the minimum y coordinate'
+        );
+        $this->addArgument(
+            'ymax',
+            InputArgument::REQUIRED,
+            'the maximum y coordinate'
+        );
+        $this->addArgument(
+            'trials',
+            InputArgument::REQUIRED,
+            'the number of trials'
+        );
+    }
+
+    #[Override]
+    protected function execute(
+        InputInterface $input,
+        OutputInterface $output
+    ): int {
+        $x_min = parse_float($input->getArgument('xmin'));
+        $x_max = parse_float($input->getArgument('xmax'));
+        $y_min = parse_float($input->getArgument('ymin'));
+        $y_max = parse_float($input->getArgument('ymax'));
+        $trials = parse_int($input->getArgument('trials'));
+
+        $x_interval = Interval1D::fromMinMax($x_min, $x_max);
+        $y_interval = Interval1D::fromMinMax($y_min, $y_max);
+        $box = \Kellegous\Algs4\Interval2D::fromXY($x_interval, $y_interval);
+        // $box->draw();
+
+        $counter = new Counter('hits');
+        $random = Random::withEngine(new Mt19937());
+        for ($i = 0; $i < $trials; $i++) {
+            $x = $random->uniformFloat();
+            $y = $random->uniformFloat();
+            $point = new Point2D($x, $y);
+            if ($box->contains($point)) {
+                $counter->increment();
+            }
+            // else $point->draw();
+        }
+
+        Stdio::out()->println($counter);
+        Stdio::out()->printf("box area = %.2f\n", $box->area());
+        return Command::SUCCESS;
+    }
+}
\ No newline at end of file
diff --git a/src/Interval2D.php b/src/Interval2D.php
index 0554e05..f2bcd93 100644
--- a/src/Interval2D.php
+++ b/src/Interval2D.php
@@ -4,14 +4,43 @@
 
 namespace Kellegous\Algs4;
 
+/**
+ *  The {@code Interval2D} class represents a closed two-dimensional interval,
+ *  which represents all points (x, y) with both {@code xmin <= x <= xmax} and
+ *  {@code ymin <= y <= ymax}.
+ *  Two-dimensional intervals are immutable: their values cannot be changed
+ *  after they are created.
+ *  The class {@code Interval2D} includes methods for checking whether
+ *  a two-dimensional interval contains a point and determining whether
+ *  two two-dimensional intervals intersect.
+ *  <p>
+ *  For additional documentation,
+ *  see <a href="https://algs4.cs.princeton.edu/12oop">Section 1.2</a> of
+ *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
+ *
+ * @author Robert Sedgewick
+ * @author Kevin Wayne
+ * @author Kelly Norton
+ */
 final readonly class Interval2D
 {
+    /**
+     * Initializes a two-dimensional interval.
+     * @param Interval1D $x
+     * @param Interval1D $y
+     */
     public function __construct(
         private Interval1D $x,
         private Interval1D $y
     ) {
     }
 
+    /**
+     * Initializes a two-dimensional interval.
+     * @param Interval1D $x
+     * @param Interval1D $y
+     * @return self
+     */
     public static function fromXY(
         Interval1D $x,
         Interval1D $y
@@ -19,29 +48,53 @@ public static function fromXY(
         return new self($x, $y);
     }
 
+    /**
+     * Does this two-dimensional interval intersect that two-dimensional interval?
+     * @param Interval2D $that
+     * @return bool
+     */
     public function intersects(self $that): bool
     {
         return $this->x->intersects($that->x)
             && $this->y->intersects($that->y);
     }
 
-    public function x(): Interval1D
+    /**
+     * Returns the area of this two-dimensional interval.
+     * @return float
+     */
+    public function area(): float
     {
-        return $this->x;
+        return $this->x->length() * $this->y->length();
     }
 
-    public function y(): Interval1D
+    /**
+     * Returns a string representation of this two-dimensional interval.
+     * @return string
+     */
+    public function __toString(): string
     {
-        return $this->y;
+        return sprintf('%s x %s', $this->x, $this->y);
     }
 
-    public function area(): float
+    /**
+     * Does this two-dimensional interval contain the point p?
+     * @param Point2D $point
+     * @return bool
+     */
+    public function contains(Point2D $point): bool
     {
-        return $this->x->length() * $this->y->length();
+        return $this->x->contains($point->x())
+            && $this->y->contains($point->y());
     }
 
-    public function __toString(): string
+    public function x(): Interval1D
     {
-        return sprintf('%s x %s', $this->x, $this->y);
+        return $this->x;
+    }
+
+    public function y(): Interval1D
+    {
+        return $this->y;
     }
 }
\ No newline at end of file
diff --git a/src/Point2D.php b/src/Point2D.php
index 0ff34b3..c6d2fad 100644
--- a/src/Point2D.php
+++ b/src/Point2D.php
@@ -4,7 +4,7 @@
 
 final readonly class Point2D
 {
-    private function __construct(
+    public function __construct(
         private float $x,
         private float $y
     ) {
diff --git a/tests/Interval2DTest.php b/tests/Interval2DTest.php
index 45d0d79..053368a 100644
--- a/tests/Interval2DTest.php
+++ b/tests/Interval2DTest.php
@@ -126,6 +126,66 @@ public static function asStringTests(): iterable
         ];
     }
 
+    /**
+     * @return iterable<string, array{Interval2D, Point2D, bool}>
+     */
+    public static function containsTests(): iterable
+    {
+        yield 'center' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(0, 0),
+            true
+        ];
+
+        yield '< x' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(-2, 0),
+            false
+        ];
+
+        yield '> x' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(2, 0),
+            false
+        ];
+
+        yield '< y' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(0, -2),
+            false
+        ];
+
+        yield '> y' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(0, 2),
+            false
+        ];
+
+        yield 'on border' => [
+            Interval2D::fromXY(
+                Interval1D::fromMinMax(-1, 1),
+                Interval1D::fromMinMax(-1, 1)
+            ),
+            Point2D::fromXY(1, 1),
+            true
+        ];
+    }
+
     /**
      * @param Interval1D $x
      * @param Interval1D $y
@@ -185,4 +245,13 @@ public function asString(
     ): void {
         self::assertEquals($expected, (string)$interval);
     }
+
+    #[Test, DataProvider('containsTests')]
+    public function contains(
+        Interval2D $interval,
+        Point2D $point,
+        bool $expected
+    ): void {
+        self::assertEquals($expected, $interval->contains($point));
+    }
 }
\ No newline at end of file