diff --git a/2d.hpp b/2d.hpp
index 444f967..71eeba5 100644
--- a/2d.hpp
+++ b/2d.hpp
@@ -32,6 +32,7 @@ struct Circle {
 
 template<int n>
 struct Polygon {
+	static_assert(n >= 3, "Polygon must have at least 3 edges");
 	std::array<Vec2, n> vertex;
 
 	Polygon() = delete;
diff --git a/test/cases/2d.cpp b/test/cases/2d.cpp
index 109d562..1eae2be 100644
--- a/test/cases/2d.cpp
+++ b/test/cases/2d.cpp
@@ -1,6 +1,7 @@
 #include "2d.hpp"
 #include "test/u.hpp"
 #include <functional>
+#include <initializer_list>
 
 namespace {
 
@@ -16,8 +17,35 @@ AddTestCase _(1, "2d.hpp", [](TestCase& t) {
 	t.expectTrue([] { return Circle({1, 1}, 1.42).contain({0, 0}); });
 
 	t.expectEq<Vec2>([] { return Polygon<3>{{0, 0}, {1, 0}, {1, 1}}.vertex[0]; }, {0, 0});
+
 	t.expectTrue([] { return Polygon<3>{{0, 0}, {1, 0}, {1, 1}}.contain({.1, .05}); });
 	t.expectFalse([] { return Polygon<3>{{0, 0}, {1, 0}, {1, 1}}.contain({.1, .2}); });
-});
 
+	Polygon<9> pA{{-2, -2}, {-1, -2}, {2, 0}, {1, -2}, {2, -1}, {2, -3}, {3, 1}, {1, 1}, {0, 0}};
+	t.expectTrue([pA] { return pA.contain({1, 0}); });
+	t.expectTrue([pA] { return pA.contain({0, 0}); });
+	t.expectTrue([pA] { return pA.contain({0, -1}); });
+	t.expectTrue([pA] { return pA.contain({1.52, -1.26}); });
+	t.expectTrue([pA] { return pA.contain({2.16, -1.9}); });
+	t.expectFalse([pA] { return pA.contain({1.28, -.8}); });
+	t.expectFalse([pA] { return pA.contain({1.68, -1.94}); });
+
+	t.expectTrue([] { return intersect(Circle({1, 1}, 2), Circle({1, 1}, 1)); });
+	t.expectTrue([] { return intersect(Circle({1, 1}, 1.5), Circle({3, 1}, 1.5)); });
+	t.expectFalse([] { return intersect(Circle({1, 1}, 1.5), Circle({3, 4}, 1.5)); });
+	t.expectFalse([] { return intersect(Circle({0, 0}, 1.5), Circle({-3, -4}, 1.5)); });
+	
+	t.expectTrue([] { return intersect(Circle({1, 1}, 2), Polygon<3>{{0, 0}, {2, 2}, {0, 2}}); });
+	t.expectTrue([] { return intersect(Polygon<3>{{0, 0}, {2, 2}, {0, 2}}, Circle({1, 1}, 2)); });
+
+	t.expectTrue([] { return intersect(Circle({0, 0}, 5), Polygon<4>{{-1, -1}, {-1, 1}, {1, 1}, {1, -1}}); });
+	t.expectTrue([] { return intersect(Circle({0, 0}, 1), Polygon<4>{{-1, -1}, {-1, 1}, {1, 1}, {1, -1}}); });
+	t.expectTrue([] { return intersect(Circle({0, 0}, 1), Polygon<4>{{-1, -1}, {-1, 1}, {1, 1}, {1, -1}}); });
+	t.expectTrue([] { return intersect(Circle({0, 0}, 1), Polygon<3>{{-1, -1}, {-1, 1}, {1, 1}}); });
+	t.expectFalse([] { return intersect(Circle({0, 0}, 2), Polygon<3>{{0, -3}, {14, -3}, {0, -5}}); });
+	t.expectFalse([pA] { return intersect(Circle({-1, 1}, 1.4), pA); });
+	t.expectTrue([pA] { return intersect(Circle({-3, -2}, 1.2), pA); });
+	t.expectTrue([pA] { return intersect(Circle({1.83649, -.07532}, .05484), pA); });
+	t.expectFalse([pA] { return intersect(Circle({1.5595, -.42437}, .08794), pA); });
+});
 }
diff --git a/test/u.hpp b/test/u.hpp
index 059c278..4c14bbb 100644
--- a/test/u.hpp
+++ b/test/u.hpp
@@ -117,17 +117,17 @@ private:
 
 	void onPass() noexcept {
 		ok += 1;
-		std::putchar('.');
+		putchar('.');
 	}
 
 	void onFail() noexcept {
 		fail += 1;
-		std::putchar('F');
+		putchar('F');
 	}
 
 	void onError() noexcept {
 		fail += 1;
-		std::putchar('E');
+		putchar('E');
 	}
 
 	template<typename T>
diff --git a/xmake.lua b/xmake.lua
index e2f3b4e..b23e643 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -12,4 +12,5 @@ target("test")
 	add_includedirs(".")
 	set_optimize("none")
 	set_symbols("debug")
-	add_defines("DEBUG")
\ No newline at end of file
+	add_defines("DEBUG")
+	set_prefixname("test-")
\ No newline at end of file