diff --git a/examples/water_2d.cpp b/examples/water_2d.cpp
new file mode 100644
index 00000000..ce22777b
--- /dev/null
+++ b/examples/water_2d.cpp
@@ -0,0 +1,485 @@
+#include <psemek/app/application_base.hpp>
+#include <psemek/app/default_application_factory.hpp>
+#include <psemek/gfx/painter.hpp>
+#include <psemek/math/orthographic.hpp>
+#include <psemek/log/log.hpp>
+#include <psemek/util/array.hpp>
+#include <psemek/random/device.hpp>
+#include <psemek/random/generator.hpp>
+#include <psemek/random/uniform.hpp>
+#include <psemek/random/uniform_sphere.hpp>
+#include <psemek/pcg/perlin.hpp>
+
+#include <format>
+
+using namespace psemek;
+
+struct water_2d_app
+	: app::application_base
+{
+	water_2d_app(options const &, context const &);
+
+	void update() override;
+	void present() override;
+
+	void on_event(app::resize_event const & event) override;
+	void on_event(app::key_event const & event) override;
+
+	math::box<float, 2> simulation_area;
+	math::box<float, 2> inner_area;
+	float aspect_ratio;
+
+	random::generator rng{random::device{}};
+
+	int const N = 128;
+
+	float time = 0.f;
+
+	util::array<float, 2> bed;
+	util::array<float, 2> water;
+	util::array<float, 2> flowx;
+	util::array<float, 2> flowy;
+	util::array<math::vector<float, 2>, 2> velocity;
+	util::array<float, 2> sediment;
+	util::array<float, 2> new_sediment;
+
+	gfx::painter painter;
+
+	bool paused = true;
+	bool show_water = true;
+	bool show_velocity = false;
+	bool erosion_on = false;
+	bool rain_on = false;
+};
+
+water_2d_app::water_2d_app(options const &, context const & ctx)
+{
+	(void)ctx;
+	ctx.vsync(true);
+
+	simulation_area[0] = {-1.f, 1.f};
+	simulation_area[1] = {-1.f, 1.f};
+
+	inner_area = math::shrink(simulation_area, simulation_area.dimensions() / (2.f * N));
+
+	bed.assign({N, N}, 0.f);
+	water.assign({N, N}, 0.f);
+	flowx.assign({N + 1, N}, 0.f);
+	flowy.assign({N, N + 1}, 0.f);
+	velocity.assign({N, N}, math::vector<float, 2>::zero());
+	sediment.assign({N, N}, 0.f);
+	new_sediment.assign({N, N}, 0.f);
+
+	// water(N / 2, N / 2) = 100.f;
+
+	random::uniform_sphere_vector_distribution<float, 2> d;
+	util::array<math::vector<float, 2>, 2> grads({9, 9});
+	for (auto & v : grads)
+		v = d(rng);
+
+	pcg::perlin<float, 2> noise(std::move(grads), pcg::seamless);
+
+	for (int y = 0; y < N; ++y)
+	{
+		for (int x = 0; x < N; ++x)
+		{
+			// if (x == N / 2 && (y != N / 4 && y != 3 * N / 4))
+			// 	bed(x, y) = 100.f;
+
+			float tx = (x + 0.5f) / N;
+			float ty = (y + 0.5f) / N;
+
+			float n = 0.f;
+
+			// Archipelago
+			n = 0.5f * noise(tx, ty) + 0.5f * noise(math::frac(2.f * tx), math::frac(2.f * ty));
+			n -= 0.5f * math::distance(math::point{tx, ty}, math::point{0.5f, 0.5f});
+			n = 5.f * math::smoothstep(math::clamp(math::unlerp({0.45f, 0.55f}, n), {0.f, 1.f}));
+
+			// Island
+			// n = 4.f * std::max(0.f, 1.f - 3.f * math::distance(math::point{tx, ty}, math::point{0.5f, 0.5f}) + (2.f * noise(tx, ty) - 1.f) * 0.25f);
+
+			// Delta
+			// n = 4.f * std::abs(2.f * noise(tx, ty) - 1.f) * (1.f - tx);
+
+			// Double delta
+			// n = 4.f * std::abs(2.f * noise(tx, ty) - 1.f) * std::pow(4.f * tx * (1.f - tx), 2.f);
+
+			// River
+			n = std::min(4.f, math::lerp(10.f, 20.f, noise(tx, ty)) * std::abs(ty - math::lerp({0.4f, 0.6f}, noise(tx, 0.f))));
+
+			// Canyon
+			// n = 10.f * math::clamp(10.f * math::lerp(-1.f, 1.f, noise(tx, ty)), {0.f, 1.f});
+
+			// Canyon v2
+			// n = math::clamp(20.f * std::abs(2.f * noise(tx, ty) - 1.f) - 2.f, {0.f, 5.f});
+
+			// Shore
+			// n = math::clamp(20.f * (ty - math::lerp(0.4f, 0.6f, noise(0.f, tx))), {-4.f, 4.f}) + 4.f;
+
+			// Circles
+			// n = 20.f * std::max(0.f, 1.f - 25.f * math::length(math::pointwise_mult({1.f, 0.1f}, math::point{tx, std::fmod(10.f * ty, 1.f)} - math::point{0.5f, 0.5f})));
+
+			bed(x, y) = n;
+
+			// water(x, y) = std::max(0.f, 4.0f - bed(x, y));
+
+			// water(x, y) = 10.f - bed(x, y);
+
+			// if (x == 0)
+			// 	water(x, y) = 100.f - bed(x, y);
+		}
+	}
+
+	// water(N / 2, N / 2) = 10000.f;
+}
+
+float const dt = 0.002f;
+
+void water_2d_app::update()
+{
+	if (paused)
+		return;
+
+	float const dx = simulation_area[0].length() / N;
+	float const dy = simulation_area[1].length() / N;
+	float const g = 10.f;
+	float const friction = std::pow(0.5f, dt);
+	float const viscosity = 0.f;
+	float const sediment_capacity = 0.1f;
+	float const erosion = 1.f;
+	float const deposition = 10.f;
+
+	// Init boundary flows
+	for (int x = 0; x < N; ++x)
+	{
+		// flowy(x, 0) = -1.f / N;
+		// flowy(x, N) =  1.f / N;
+
+		// if (x >= 3 * N / 4) flowy(x, 0) = 3.f / N;
+		// if (x < N / 4) flowy(x, N) = -3.f / N;
+
+		// flowy(x, 0) = 5.f * std::sin(10.f * time) / N;
+	}
+
+	for (int y = 0; y < N; ++y)
+	{
+		// flowx(0, y) =  5.f * std::sin(10.f * time) / N;
+
+		// flowx(0, y) =  1.f / N;
+		// flowx(N, y) =  1.f / N;
+
+		// flowx(0, y) = 10.f * ((y + 0.5f) / N) / N;
+		// flowx(N, y) = - (10.f / N - flowx(0, y));
+
+		// if (y < N / 4) flowx(0, y) = 3.f / N;
+		// if (y >= 3 * N / 4) flowx(N, y) = -3.f / N;
+
+		if (bed(0, y) < 0.75f)
+			flowx(0, y) = 4.f / N;
+			// flowx(0, y) = 5.f * math::sqr(std::max(0.f, std::sin(15.f * time))) / N;
+
+		if (bed(N - 1, y) < 0.75f)
+			flowx(N, y) = 5.f / N;
+	}
+
+	// Rain :)
+	if (rain_on)
+		for (int y = 0; y < N; ++y)
+			for (int x = 0; x < N; ++x)
+				// if (random::uniform<float>(rng) < 0.1f)
+					water(x, y) += random::uniform<float>(rng) * dt;
+					// water(x, y) += dt;
+
+	// water(N/2, N/2) += 1000.f * dt;
+
+	// Update X flows
+	for (int y = 0; y < N; ++y)
+		for (int x = 1; x < N; ++x)
+			flowx(x, y) = friction * flowx(x, y) + g * dt * (water(x - 1, y) + bed(x - 1, y) - water(x, y) - bed(x, y));
+
+	// Update Y flows
+	for (int y = 1; y < N; ++y)
+		for (int x = 0; x < N; ++x)
+			flowy(x, y) = friction * flowy(x, y) + g * dt * (water(x, y - 1) + bed(x, y - 1) - water(x, y) - bed(x, y));
+
+	// Apply viscosity to X flows
+	for (int y = 0; y < N; ++y)
+	{
+		for (int x = 1; x < N; ++x)
+		{
+			float h = (flowx(x, y) > 0.f) ? water(x - 1, y) : water(x, y);
+			h *= h;
+
+			if (h > 0.f)
+				flowx(x, y) *= h / (h + 3.f * dt * viscosity);
+		}
+	}
+
+	// Apply viscosity to Y flows
+	for (int y = 1; y < N; ++y)
+	{
+		for (int x = 0; x < N; ++x)
+		{
+			float h = (flowy(x, y) > 0.f) ? water(x, y - 1) : water(x, y);
+			h *= h;
+
+			if (h > 0.f)
+				flowy(x, y) *= h / (h + 3.f * dt * viscosity);
+		}
+	}
+
+	// Scale flows
+	for (int y = 0; y < N; ++y)
+	{
+		for (int x = 0; x < N; ++x)
+		{
+			float outflow = 0.f;
+			outflow += std::max(0.f, - flowx(x    , y    ));
+			outflow += std::max(0.f,   flowx(x + 1, y    ));
+			outflow += std::max(0.f, - flowy(x    , y    ));
+			outflow += std::max(0.f,   flowy(x    , y + 1));
+
+			float max_outflow = water(x, y) * dx * dy / dt;
+
+			if (outflow > 0.f)
+			{
+				float scale = std::min(1.f, max_outflow / outflow);
+
+				if (flowx(x, y) < 0.f) flowx(x, y) *= scale;
+				if (flowx(x + 1, y) > 0.f) flowx(x + 1, y) *= scale;
+
+				if (flowy(x, y) < 0.f) flowy(x, y) *= scale;
+				if (flowy(x, y + 1) > 0.f) flowy(x, y + 1) *= scale;
+			}
+		}
+	}
+
+	// Update water and compute velocity
+	for (int y = 0; y < N; ++y)
+	{
+		for (int x = 0; x < N; ++x)
+		{
+			float w_old = water(x, y);
+
+			water(x, y) += dt / dx / dy * (flowx(x, y) + flowy(x, y) - flowx(x + 1, y) - flowy(x, y + 1));
+
+			float w_avg = (w_old + water(x, y)) / 2.f;
+
+			math::vector v{0.f, 0.f};
+
+			if (w_avg > 0.f)
+			{
+				v[0] = (flowx(x, y) + flowx(x + 1, y)) / 2.f / dx / w_avg;
+				v[1] = (flowy(x, y) + flowy(x, y + 1)) / 2.f / dy / w_avg;
+			}
+
+			velocity(x, y) = v;
+		}
+	}
+
+	if (erosion_on)
+	{
+		// Erosion-deposition
+		for (int y = 0; y < N; ++y)
+		{
+			for (int x = 0; x < N; ++x)
+			{
+				float c = sediment_capacity * water(x, y) * math::length(velocity(x, y));
+
+				if (c >= sediment(x, y))
+				{
+					float delta = std::min(bed(x, y), dt * erosion * (c - sediment(x, y)));
+					bed(x, y) -= delta;
+					sediment(x, y) += delta;
+				}
+				else
+				{
+					float delta = std::min(sediment(x, y), dt * deposition * (sediment(x, y) - c));
+					bed(x, y) += delta;
+					sediment(x, y) -= delta;
+				}
+			}
+		}
+
+		// Sediment transport
+		for (int y = 0; y < N; ++y)
+		{
+			for (int x = 0; x < N; ++x)
+			{
+				math::point p = math::lerp(simulation_area, {(x + 0.5f) / N, (y + 0.5f) / N});
+				p -= velocity(x, y) * dt;
+
+				p = math::clamp(p, inner_area);
+
+				auto q = math::unlerp(inner_area, p) * (N - 1.f);
+
+				int ix = std::min<int>(N - 2, std::floor(q[0]));
+				int iy = std::min<int>(N - 2, std::floor(q[1]));
+
+				float tx = q[0] - ix;
+				float ty = q[1] - iy;
+
+				new_sediment(x, y) = 0.f
+					+ sediment(ix, iy) * (1.f - tx) * (1.f - ty)
+					+ sediment(ix + 1, iy) * tx * (1.f - ty)
+					+ sediment(ix, iy + 1) * (1.f - tx) * ty
+					+ sediment(ix + 1, iy + 1) * tx * ty
+					;
+			}
+		}
+
+		std::swap(sediment, new_sediment);
+	}
+
+	time += dt;
+}
+
+void water_2d_app::present()
+{
+	gl::ClearColor(0.8f, 0.8f, 0.8f, 0.8f);
+	gl::Clear(gl::COLOR_BUFFER_BIT);
+
+	math::box<float, 3> view_area;
+	{
+		view_area[0] = simulation_area[0];
+		view_area[1] = simulation_area[1];
+		view_area[2] = {-1.f, 1.f};
+
+		float extra_y = view_area[1].length() * 0.f;
+		view_area[1].min -= extra_y;
+		view_area[1].max += extra_y;
+		float extra_x = view_area[1].length() * aspect_ratio - view_area[0].length();
+		view_area[0].min -= extra_x / 2.f;
+		view_area[0].max += extra_x / 2.f;
+	}
+
+	math::matrix<float, 4, 4> const transform = math::orthographic{view_area}.homogeneous_matrix();
+
+	painter.rect(simulation_area, {0, 0, 0, 255});
+
+	float invN = 1.f / N;
+
+	for (int y = 0; y < N; ++y)
+	{
+		for (int x = 0; x < N; ++x)
+		{
+			auto min = simulation_area.corner(x * invN, y * invN);
+			auto max = simulation_area.corner((x + 1) * invN, (y + 1) * invN);
+
+			float b = 1.f - std::exp(- 1.f * bed(x, y));
+			float w = 1.f - std::exp(- 1.f * water(x, y));
+			float s = 1.f - std::exp(- 1.f * sediment(x, y));
+
+			if (water(x, y) > 1e-3f)
+				w = 0.5f + 0.5f * w;
+
+			auto bed_color = gfx::to_coloru8(gfx::color_4f{0.96f, 0.72f, 0.53f, b});
+			// auto bed_color = gfx::to_coloru8(gfx::color_4f{0.3f, 0.5f, 0.1f, b});
+			auto color = gfx::to_coloru8(gfx::color_4f{0.f, 0.25f, 1.f, w});
+			auto sediment_color = gfx::to_coloru8(gfx::color_4f{1.f, 0.25f, 0.f, s * w});
+
+			auto box = math::box<float, 2>::singleton(min) | math::box<float, 2>::singleton(max);
+
+			painter.rect(box, bed_color);
+			if (show_water)
+			{
+				painter.rect(box, color);
+				painter.rect(box, sediment_color);
+			}
+		}
+	}
+
+	if (show_velocity)
+	{
+		for (int y = 0; y < N; ++y)
+		{
+			for (int x = 0; x < N; ++x)
+			{
+				auto center = simulation_area.corner((x + 0.5f) * invN, (y + 0.5f) * invN);
+
+				auto v = water(x, y) * velocity(x, y) / 100.f;
+
+				float max_length = 0.02f;
+				auto l = math::length(v);
+
+				auto color = gfx::to_coloru8(gfx::color_4f{1.f, std::exp(- 10.f * l), 0.f, 1.f});
+
+				float s = std::min(1.f, l / max_length);
+
+				painter.line(center, center + math::normalized(v) * max_length * s, s * 0.004f, s * 0.002f, color, color, false);
+			}
+		}
+	}
+
+	auto mouse = math::cast<float>(state().mouse);
+
+	mouse[0] = math::lerp(view_area[0], mouse[0] / state().size[0]);
+	mouse[1] = math::lerp(view_area[1], 1.f - mouse[1] / state().size[1]);
+
+	int mx = std::floor(N * math::unlerp(simulation_area[0], mouse[0]));
+	int my = std::floor(N * math::unlerp(simulation_area[1], mouse[1]));
+
+	if (mx >= 0 && mx < N && my >= 0 && my < N)
+	{
+		gfx::painter::text_options opts
+		{
+			.scale = {0.004f, -0.004f},
+			.c = {255, 0, 255, 255},
+		};
+		painter.text({view_area[0].center(), math::lerp(view_area[1], 0.03f)}, std::format("b {:.3f} + w {:.3f} = h {:.3f}", bed(mx, my), water(mx, my), bed(mx, my) + water(mx, my)), opts);
+		painter.text({view_area[0].center(), math::lerp(view_area[1], 0.05f)}, std::format("s {:.3f}", sediment(mx, my)), opts);
+
+		if (state().mouse_button_down.contains(app::mouse_button::left))
+		{
+			for (int dy = -2; dy <= 2; ++dy)
+			{
+				for (int dx = -2; dx <= 2; ++dx)
+				{
+					int x = mx + dx;
+					int y = my + dy;
+
+					if (x >= 0 && x < N && y >= 0 && y < N)
+						water(x, y) += 1000.f * dt;
+				}
+			}
+		}
+	}
+
+	painter.render(transform);
+}
+
+void water_2d_app::on_event(app::resize_event const & event)
+{
+	app::application_base::on_event(event);
+
+	aspect_ratio = (event.size[0] * 1.f) / event.size[1];
+}
+
+void water_2d_app::on_event(app::key_event const & event)
+{
+	if (event.down && event.key == app::keycode::SPACE)
+		paused ^= true;
+
+	if (event.down && event.key == app::keycode::W)
+		show_water ^= true;
+
+	if (event.down && event.key == app::keycode::V)
+		show_velocity ^= true;
+
+	if (event.down && event.key == app::keycode::E)
+		erosion_on ^= true;
+
+	if (event.down && event.key == app::keycode::R)
+		rain_on ^= true;
+}
+
+namespace psemek::app
+{
+
+	std::unique_ptr<application::factory> make_application_factory()
+	{
+		return default_application_factory<water_2d_app>({.name = "Water 2D example", .multisampling = 4});
+	}
+
+}