diff --git a/src/game/game.rs b/src/game/game.rs
index 6320a98..23e1369 100644
--- a/src/game/game.rs
+++ b/src/game/game.rs
@@ -2,13 +2,14 @@ use cgmath::Deg;
 use std::time::Instant;
 use winit::event::{ElementState, MouseButton, MouseScrollDelta, TouchPhase, VirtualKeyCode};
 
-use super::{ship::ShipKind, Camera, InputStatus, Ship, System};
+use super::{Camera, InputStatus, Ship, System};
 use crate::{consts, content::Content, render::Sprite, render::Spriteable};
 
 pub struct Game {
 	pub input: InputStatus,
 	pub last_update: Instant,
 	pub player: Ship,
+	pub test: Ship,
 	pub system: System,
 	pub camera: Camera,
 	paused: bool,
@@ -20,7 +21,7 @@ impl Game {
 		Game {
 			last_update: Instant::now(),
 			input: InputStatus::new(),
-			player: Ship::new(ShipKind::Gypsum, (0.0, 0.0).into()),
+			player: Ship::new(&ct.ships[0], (0.0, 0.0).into()),
 			camera: Camera {
 				pos: (0.0, 0.0).into(),
 				zoom: 500.0,
@@ -28,6 +29,7 @@ impl Game {
 			system: System::new(&ct.systems[0]),
 			paused: false,
 			time_scale: 1.0,
+			test: Ship::new(&ct.ships[0], (100.0, 100.0).into()),
 		}
 	}
 
@@ -55,6 +57,7 @@ impl Game {
 	pub fn update(&mut self) {
 		let t: f32 = self.last_update.elapsed().as_secs_f32() * self.time_scale;
 
+		self.player.engines_on = self.input.key_thrust;
 		if self.input.key_thrust {
 			self.player.physicsbody.thrust(50.0 * t);
 		}
@@ -84,11 +87,13 @@ impl Game {
 
 		sprites.append(&mut self.system.get_sprites());
 		sprites.push(self.player.get_sprite());
+		sprites.push(self.test.get_sprite());
 
 		// Make sure sprites are drawn in the correct order
 		// (note the reversed a, b in the comparator)
 		//
-		// TODO: use a gpu depth buffer instead.
+		// TODO: maybe use a gpu depth buffer instead?
+		// I've tried this, but it doesn't seem to work with transparent textures.
 		sprites.sort_by(|a, b| b.pos.z.total_cmp(&a.pos.z));
 
 		return sprites;
diff --git a/src/game/ship.rs b/src/game/ship.rs
index 382e2f8..f76adba 100644
--- a/src/game/ship.rs
+++ b/src/game/ship.rs
@@ -1,49 +1,63 @@
-use cgmath::Point2;
+use cgmath::{Deg, Point2, Point3};
 
-use crate::{physics::PhysicsBody, render::Sprite, render::SpriteTexture, render::Spriteable};
-
-pub enum ShipKind {
-	Gypsum,
-}
-
-impl ShipKind {
-	fn sprite(&self) -> SpriteTexture {
-		let name = match self {
-			Self::Gypsum => "ship::gypsum",
-		};
-
-		return SpriteTexture(name.to_owned());
-	}
-
-	fn size(&self) -> f32 {
-		match self {
-			Self::Gypsum => 100.0,
-		}
-	}
-}
+use crate::{
+	content::{self, ship::Engine},
+	physics::PhysicsBody,
+	render::Sprite,
+	render::SpriteTexture,
+	render::Spriteable,
+};
 
 pub struct Ship {
 	pub physicsbody: PhysicsBody,
-	kind: ShipKind,
+	pub engines_on: bool,
+
+	sprite: SpriteTexture,
+	size: f32,
+	engines: Vec<Engine>,
 }
 
 impl Ship {
-	pub fn new(kind: ShipKind, pos: Point2<f32>) -> Self {
+	pub fn new(ct: &content::ship::Ship, pos: Point2<f32>) -> Self {
 		Ship {
 			physicsbody: PhysicsBody::new(pos),
-			kind,
+			sprite: SpriteTexture(ct.sprite.clone()),
+			size: ct.size,
+			engines: ct.engines.clone(),
+			engines_on: false,
 		}
 	}
 }
 
 impl Spriteable for Ship {
 	fn get_sprite(&self) -> Sprite {
-		return Sprite {
-			pos: (self.physicsbody.pos.x, self.physicsbody.pos.y, 1.0).into(),
-			texture: self.kind.sprite(),
-			angle: self.physicsbody.angle,
-			scale: 1.0,
-			size: self.kind.size(),
+		let engines = if self.engines_on {
+			Some(
+				self.engines
+					.iter()
+					.map(|e| Sprite {
+						pos: Point3 {
+							x: e.pos.x,
+							y: e.pos.y,
+							z: 1.0,
+						},
+						texture: SpriteTexture("flare::ion".to_owned()),
+						angle: Deg(0.0),
+						size: e.size,
+						children: None,
+					})
+					.collect(),
+			)
+		} else {
+			None
 		};
+
+		Sprite {
+			pos: (self.physicsbody.pos.x, self.physicsbody.pos.y, 1.0).into(),
+			texture: self.sprite.clone(), // TODO: sprite texture should be easy to clone
+			angle: self.physicsbody.angle,
+			size: self.size,
+			children: engines,
+		}
 	}
 }
diff --git a/src/game/system.rs b/src/game/system.rs
index 2e4f852..270cf7a 100644
--- a/src/game/system.rs
+++ b/src/game/system.rs
@@ -2,7 +2,7 @@ use cgmath::{Point3, Vector2};
 use rand::{self, Rng};
 
 use super::SystemObject;
-use crate::{consts, content, render::Sprite, render::SpriteTexture, render::Spriteable};
+use crate::{consts, content, render::Sprite, render::SpriteTexture};
 
 pub struct StarfieldStar {
 	/// Star coordinates, in world space.
diff --git a/src/game/systemobject.rs b/src/game/systemobject.rs
index f43b2ff..5b73365 100644
--- a/src/game/systemobject.rs
+++ b/src/game/systemobject.rs
@@ -1,6 +1,6 @@
 use cgmath::{Deg, Point3};
 
-use crate::{render::Sprite, render::SpriteTexture, render::Spriteable};
+use crate::{render::Sprite, render::SpriteTexture};
 
 pub struct SystemObject {
 	pub sprite: SpriteTexture,
@@ -9,14 +9,14 @@ pub struct SystemObject {
 	pub angle: Deg<f32>,
 }
 
-impl Spriteable for SystemObject {
-	fn get_sprite(&self) -> Sprite {
+impl SystemObject {
+	pub(super) fn get_sprite(&self) -> Sprite {
 		return Sprite {
 			texture: self.sprite.clone(),
-			scale: 1.0,
 			pos: self.pos,
 			angle: self.angle,
 			size: self.size,
+			children: None,
 		};
 	}
 }
diff --git a/src/render/consts.rs b/src/render/consts.rs
index 9a3affb..9fd4d2f 100644
--- a/src/render/consts.rs
+++ b/src/render/consts.rs
@@ -1,4 +1,5 @@
 use crate::consts;
+use cgmath::Matrix4;
 
 // We can draw at most this many sprites on the screen.
 // TODO: compile-time option
@@ -16,3 +17,11 @@ pub const TEXTURE_INDEX_PATH: &'static str = "./assets";
 /// Shader entry points
 pub const SHADER_MAIN_VERTEX: &'static str = "vertex_main";
 pub const SHADER_MAIN_FRAGMENT: &'static str = "fragment_main";
+
+#[rustfmt::skip]
+pub const OPENGL_TO_WGPU_MATRIX: Matrix4<f32> = Matrix4::new(
+	1.0, 0.0, 0.0, 0.0,
+	0.0, 1.0, 0.0, 0.0,
+	0.0, 0.0, 0.5, 0.5,
+	0.0, 0.0, 0.0, 1.0,
+);
diff --git a/src/render/gpustate.rs b/src/render/gpustate.rs
index 0758365..d298b8c 100644
--- a/src/render/gpustate.rs
+++ b/src/render/gpustate.rs
@@ -1,12 +1,12 @@
 use anyhow::Result;
 use bytemuck;
-use cgmath::{EuclideanSpace, Matrix2, Point2, Vector2, Vector3};
+use cgmath::{Deg, EuclideanSpace, Matrix4, Point2, Vector2, Vector3};
 use std::{iter, rc::Rc};
 use wgpu;
 use winit::{self, dpi::PhysicalSize, window::Window};
 
 use super::{
-	consts::{SPRITE_INSTANCE_LIMIT, STARFIELD_INSTANCE_LIMIT},
+	consts::{OPENGL_TO_WGPU_MATRIX, SPRITE_INSTANCE_LIMIT, STARFIELD_INSTANCE_LIMIT},
 	globaldata::{GlobalData, GlobalDataContent},
 	pipeline::PipelineBuilder,
 	texturearray::TextureArray,
@@ -15,6 +15,7 @@ use super::{
 		types::{SpriteInstance, StarfieldInstance, TexturedVertex},
 		VertexBuffer,
 	},
+	Sprite,
 };
 use crate::{consts, game::Game};
 
@@ -194,6 +195,138 @@ impl GPUState {
 		self.update_starfield_buffer(game)
 	}
 
+	/// Create a SpriteInstance for s and add it to instances.
+	/// Also handles child sprites.
+	fn push_sprite(
+		&self,
+		game: &Game,
+		instances: &mut Vec<SpriteInstance>,
+		clip_ne: Point2<f32>,
+		clip_sw: Point2<f32>,
+		s: Sprite,
+	) {
+		// Position adjusted for parallax
+		// TODO: adjust parallax for zoom?
+		let pos: Point2<f32> = {
+			(Point2 {
+				x: s.pos.x,
+				y: s.pos.y,
+			} - game.camera.pos.to_vec())
+				/ s.pos.z
+		};
+		let texture = self.texture_array.get_sprite_texture(s.texture);
+
+		// Game dimensions of this sprite post-scale.
+		// Don't divide by 2, we use this later.
+		let height = s.size / s.pos.z;
+		let width = height * texture.aspect;
+
+		// Don't draw (or compute matrices for)
+		// sprites that are off the screen
+		if pos.x < clip_ne.x - width
+			|| pos.y > clip_ne.y + height
+			|| pos.x > clip_sw.x + width
+			|| pos.y < clip_sw.y - height
+		{
+			return;
+		}
+
+		// TODO: clean up
+		let scale = height / game.camera.zoom;
+
+		// Note that our mesh starts centered at (0, 0).
+		// This is essential---we do not want scale and rotation
+		// changing our sprite's position!
+
+		// Apply sprite aspect ratio, preserving height.
+		// This must be done *before* rotation.
+		//
+		// We apply the provided scale here as well as a minor optimization
+		let sprite_aspect_and_scale =
+			Matrix4::from_nonuniform_scale(texture.aspect * scale, scale, 1.0);
+
+		// Apply rotation
+		let rotate = Matrix4::from_angle_z(s.angle);
+
+		// Apply screen aspect ratio, again preserving height.
+		// This must be done AFTER rotation... think about it!
+		let screen_aspect = Matrix4::from_nonuniform_scale(1.0 / self.window_aspect, 1.0, 1.0);
+
+		// After finishing all ops, translate.
+		// This must be done last, all other operations
+		// require us to be at (0, 0).
+		let translate = Matrix4::from_translation(Vector3 {
+			x: pos.x / game.camera.zoom / self.window_aspect,
+			y: pos.y / game.camera.zoom,
+			z: 0.0,
+		});
+
+		// Order matters!
+		// The rightmost matrix is applied first.
+		let t =
+			OPENGL_TO_WGPU_MATRIX * translate * screen_aspect * rotate * sprite_aspect_and_scale;
+
+		instances.push(SpriteInstance {
+			transform: t.into(),
+			texture_index: texture.index,
+		});
+
+		// Add children
+		if let Some(children) = s.children {
+			for c in children {
+				self.push_subsprite(game, instances, c, pos, s.angle);
+			}
+		}
+	}
+
+	/// Add a sprite's subsprite to instance.
+	/// Only called by push_sprite.
+	fn push_subsprite(
+		&self,
+		game: &Game,
+		instances: &mut Vec<SpriteInstance>,
+		s: Sprite,
+		parent_pos: Point2<f32>,
+		parent_angle: Deg<f32>,
+	) {
+		// TODO: clean up
+		if s.children.is_some() {
+			panic!("Child sprites must not have child sprites!")
+		}
+
+		let texture = self.texture_array.get_sprite_texture(s.texture);
+		let scale = s.size / (s.pos.z * game.camera.zoom);
+		let sprite_aspect_and_scale =
+			Matrix4::from_nonuniform_scale(texture.aspect * scale, scale, 1.0);
+		let rotate = Matrix4::from_angle_z(s.angle);
+		let screen_aspect = Matrix4::from_nonuniform_scale(1.0 / self.window_aspect, 1.0, 1.0);
+
+		let ptranslate = Matrix4::from_translation(Vector3 {
+			x: parent_pos.x / game.camera.zoom / self.window_aspect,
+			y: parent_pos.y / game.camera.zoom,
+			z: 0.0,
+		});
+		let protate = Matrix4::from_angle_z(parent_angle);
+
+		let translate = Matrix4::from_translation(Vector3 {
+			x: s.pos.x / game.camera.zoom / self.window_aspect,
+			y: s.pos.y / game.camera.zoom,
+			z: 0.0,
+		});
+
+		// Order matters!
+		// The rightmost matrix is applied first.
+		let t = OPENGL_TO_WGPU_MATRIX
+			* ptranslate * screen_aspect
+			* protate * translate
+			* rotate * sprite_aspect_and_scale;
+
+		instances.push(SpriteInstance {
+			transform: t.into(),
+			texture_index: texture.index,
+		});
+	}
+
 	/// Make a SpriteInstance for each of the game's visible sprites.
 	/// Will panic if SPRITE_INSTANCE_LIMIT is exceeded.
 	///
@@ -207,45 +340,13 @@ impl GPUState {
 		let clip_sw = Point2::from((self.window_aspect, -1.0)) * game.camera.zoom;
 
 		for s in game.get_sprites() {
-			// Compute post-parallax position and distance-adjusted scale.
-			// We do this here so we can check if a sprite is on the screen.
-			let pos: Point2<f32> = {
-				(Point2 {
-					x: s.pos.x,
-					y: s.pos.y,
-				} - game.camera.pos.to_vec())
-					/ (s.pos.z + game.camera.zoom / consts::ZOOM_MIN)
-			};
-			let texture = self.texture_array.get_sprite_texture(s.texture);
-
-			// Game dimensions of this sprite post-scale.
-			// Don't divide by 2, we use this later.
-			let height = s.size * s.scale / s.pos.z;
-			let width = height * texture.aspect;
-
-			// Don't draw (or compute matrices for)
-			// sprites that are off the screen
-			if pos.x < clip_ne.x - width
-				|| pos.y > clip_ne.y + height
-				|| pos.x > clip_sw.x + width
-				|| pos.y < clip_sw.y - height
-			{
-				continue;
-			}
-
-			instances.push(SpriteInstance {
-				position: pos.into(),
-				aspect: texture.aspect,
-				rotation: Matrix2::from_angle(s.angle).into(),
-				size: height,
-				texture_index: texture.index,
-			})
+			self.push_sprite(game, &mut instances, clip_ne, clip_sw, s);
 		}
 
 		// Enforce sprite limit
 		if instances.len() as u64 > SPRITE_INSTANCE_LIMIT {
 			// TODO: no panic, handle this better.
-			unreachable!("Sprite limit exceeded!")
+			panic!("Sprite limit exceeded!")
 		}
 
 		return instances;
diff --git a/src/render/mod.rs b/src/render/mod.rs
index 30317c5..445ba36 100644
--- a/src/render/mod.rs
+++ b/src/render/mod.rs
@@ -12,16 +12,3 @@ pub use sprite::{Sprite, Spriteable};
 /// A handle to a sprite texture
 #[derive(Debug, Clone)]
 pub struct SpriteTexture(pub String);
-
-/*
-// API correction matrix.
-// cgmath uses OpenGL's matrix format, which
-// needs to be converted to wgpu's matrix format.
-#[rustfmt::skip]
-const OPENGL_TO_WGPU_MATRIX: Matrix4<f32> = Matrix4::new(
-	1.0, 0.0, 0.0, 0.0,
-	0.0, 1.0, 0.0, 0.0,
-	0.0, 0.0, 0.5, 0.5,
-	0.0, 0.0, 0.0, 1.0,
-);
-*/
diff --git a/src/render/shaders/sprite.wgsl b/src/render/shaders/sprite.wgsl
index 9a5b78a..ea6de70 100644
--- a/src/render/shaders/sprite.wgsl
+++ b/src/render/shaders/sprite.wgsl
@@ -1,10 +1,9 @@
 struct InstanceInput {
-	@location(2) rotation_matrix_0: vec2<f32>,
-	@location(3) rotation_matrix_1: vec2<f32>,
-	@location(4) position: vec2<f32>,
-	@location(5) size: f32,
-	@location(6) aspect: f32,
-	@location(7) texture_idx: u32,
+	@location(2) transform_matrix_0: vec4<f32>,
+	@location(3) transform_matrix_1: vec4<f32>,
+	@location(4) transform_matrix_2: vec4<f32>,
+	@location(5) transform_matrix_3: vec4<f32>,
+	@location(6) texture_idx: u32,
 };
 
 struct VertexInput {
@@ -47,33 +46,15 @@ fn vertex_main(
 	instance: InstanceInput,
 ) -> VertexOutput {
 
-	// Apply sprite aspect ratio & scale factor
-	// This must be done *before* rotation.
-	let scale = instance.size / global.camera_zoom.x;
-	var pos: vec2<f32> = vec2<f32>(
-		vertex.position.x * instance.aspect * scale,
-		vertex.position.y * scale
-	);
-
-	// Rotate
-	pos = mat2x2<f32>(
-		instance.rotation_matrix_0,
-		instance.rotation_matrix_1,
-	) * pos;
-
-	// Apply screen aspect ratio, again preserving height.
-	// This must be done AFTER rotation... think about it!
-	pos = pos / vec2<f32>(global.window_aspect.x, 1.0);
-
-	// Translate
-	pos = pos + (
-		// Don't forget to correct distance for screen aspect ratio too!
-		(instance.position / global.camera_zoom.x)
-		/ vec2<f32>(global.window_aspect.x, 1.0)
+	let transform = mat4x4<f32>(
+		instance.transform_matrix_0,
+		instance.transform_matrix_1,
+		instance.transform_matrix_2,
+		instance.transform_matrix_3,
 	);
 
 	var out: VertexOutput;
-	out.position = vec4<f32>(pos, 0.0, 1.0);
+	out.position = transform * vec4<f32>(vertex.position, 1.0);
 	out.texture_coords = vertex.texture_coords;
 	out.index = instance.texture_idx;
 	return out;
diff --git a/src/render/sprite.rs b/src/render/sprite.rs
index f597a22..3a85248 100644
--- a/src/render/sprite.rs
+++ b/src/render/sprite.rs
@@ -13,13 +13,18 @@ pub struct Sprite {
 	/// given as height in world units.
 	pub size: f32,
 
-	/// Scale factor.
-	/// if this is 1, sprite height is exactly self.size.
-	pub scale: f32,
-
 	/// This sprite's rotation
 	/// (relative to north, measured ccw)
 	pub angle: Deg<f32>,
+
+	/// Sprites that should be drawn relative to this sprite.
+	/// Coordinates of sprites in this array will be interpreted
+	/// as world units, relative to the center of this sprite,
+	/// before any rotation or scaling.
+	/// Children rotate with their parent sprite.
+	///
+	/// Note that child sprites may NOT have children.
+	pub children: Option<Vec<Sprite>>,
 }
 
 pub trait Spriteable {
diff --git a/src/render/vertexbuffer/types.rs b/src/render/vertexbuffer/types.rs
index 3ba17ab..de03ca4 100644
--- a/src/render/vertexbuffer/types.rs
+++ b/src/render/vertexbuffer/types.rs
@@ -86,20 +86,9 @@ impl BufferObject for StarfieldInstance {
 #[repr(C)]
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct SpriteInstance {
-	/// Rotation matrix for this sprite
-	pub rotation: [[f32; 2]; 2],
-
-	/// World position, relative to camera
-	/// Note that this does NOT contain z-distance,
-	/// since sprite parallax and distance scaling
-	/// is applied beforehand.
-	pub position: [f32; 2],
-
-	/// Height of (unrotated) sprite in world units
-	pub size: f32,
-
-	// Sprite aspect ratio (width / height)
-	pub aspect: f32,
+	/// Extra transformations this sprite
+	/// (rotation, etc)
+	pub transform: [[f32; 4]; 4],
 
 	// What texture to use for this sprite
 	pub texture_index: u32,
@@ -114,39 +103,31 @@ impl BufferObject for SpriteInstance {
 			// instance when the shader starts processing a new instance
 			step_mode: wgpu::VertexStepMode::Instance,
 			attributes: &[
-				// 2 arrays = 1 2x2 matrix
+				// 4 arrays = 1 4x4 matrix
 				wgpu::VertexAttribute {
 					offset: 0,
 					shader_location: 2,
-					format: wgpu::VertexFormat::Float32x2,
+					format: wgpu::VertexFormat::Float32x4,
 				},
-				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 2]>() as wgpu::BufferAddress,
-					shader_location: 3,
-					format: wgpu::VertexFormat::Float32x2,
-				},
-				// Position
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
+					shader_location: 3,
+					format: wgpu::VertexFormat::Float32x4,
+				},
+				wgpu::VertexAttribute {
+					offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
 					shader_location: 4,
-					format: wgpu::VertexFormat::Float32x2,
+					format: wgpu::VertexFormat::Float32x4,
 				},
-				// Size
 				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 6]>() as wgpu::BufferAddress,
+					offset: mem::size_of::<[f32; 12]>() as wgpu::BufferAddress,
 					shader_location: 5,
-					format: wgpu::VertexFormat::Float32,
-				},
-				// Aspect
-				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 7]>() as wgpu::BufferAddress,
-					shader_location: 6,
-					format: wgpu::VertexFormat::Float32,
+					format: wgpu::VertexFormat::Float32x4,
 				},
 				// Texture
 				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
-					shader_location: 7,
+					offset: mem::size_of::<[f32; 16]>() as wgpu::BufferAddress,
+					shader_location: 6,
 					format: wgpu::VertexFormat::Uint32,
 				},
 			],