diff --git a/src/GL.cc b/src/GL.cc
index 391d6e2..6c99487 100644
--- a/src/GL.cc
+++ b/src/GL.cc
@@ -22,9 +22,31 @@ static VALUE ruby_module;
 static GLBufferRef rect_buffer;
 static GLProgram * programs[PROGRAM_COUNT];
 
+static VALUE GL_draw_rect(VALUE klass,
+                          VALUE x, VALUE y, VALUE width, VALUE height,
+                          VALUE r, VALUE g, VALUE b, VALUE a)
+{
+    glUseProgram(programs[PROGRAM_RECT]->id);
+    glUniform2i(programs[PROGRAM_RECT]->uniforms[UNIFORM_POSITION], FIX2INT(x), FIX2INT(y));
+    glUniform2i(programs[PROGRAM_RECT]->uniforms[UNIFORM_SIZE], FIX2INT(width), FIX2INT(height));
+    glUniform4f(programs[PROGRAM_RECT]->uniforms[UNIFORM_COLOR],
+                RFLOAT_VALUE(r),
+                RFLOAT_VALUE(g),
+                RFLOAT_VALUE(b),
+                RFLOAT_VALUE(a));
+    rect_buffer->bind();
+    glEnableVertexAttribArray(0);
+    glVertexAttribIPointer(0, 2, GL_INT, 0, 0);
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+
+    return Qnil;
+}
+
 void GL_Init()
 {
     ruby_module = rb_define_module("GL");
+    rb_define_singleton_method(ruby_module, "draw_rect",
+                               (VALUE(*)(...))GL_draw_rect, 4);
 }
 
 static void load_gl_buffers()