diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb2673f..9e89cc4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -218,6 +218,8 @@ set_target_properties(flite PROPERTIES FOLDER lib)
 
 # ... rhubarb-animation
 add_library(rhubarb-animation
+	src/animation/animationRules.cpp
+	src/animation/animationRules.h
 	src/animation/mouthAnimation.cpp
 	src/animation/mouthAnimation.h
 	src/animation/Viseme.cpp
diff --git a/src/animation/animationRules.cpp b/src/animation/animationRules.cpp
new file mode 100644
index 0000000..54899a7
--- /dev/null
+++ b/src/animation/animationRules.cpp
@@ -0,0 +1,96 @@
+#include "animationRules.h"
+#include <boost/algorithm/clamp.hpp>
+
+using std::chrono::duration_cast;
+using boost::algorithm::clamp;
+using boost::optional;
+
+constexpr Shape A = Shape::A;
+constexpr Shape B = Shape::B;
+constexpr Shape C = Shape::C;
+constexpr Shape D = Shape::D;
+constexpr Shape E = Shape::E;
+constexpr Shape F = Shape::F;
+constexpr Shape G = Shape::G;
+constexpr Shape H = Shape::H;
+constexpr Shape X = Shape::X;
+
+Timeline<ShapeSet> animatePhone(optional<Phone> phone, centiseconds duration, centiseconds previousDuration) {
+	// Returns a timeline with a single shape set
+	auto single = [&](ShapeSet value) {
+		return Timeline<ShapeSet> { { 0_cs, duration, value } };
+	};
+
+	// Returns a timeline with two shape sets, timed as a diphthong
+	auto diphthong = [&](ShapeSet first, ShapeSet second) {
+		centiseconds firstDuration = duration_cast<centiseconds>(duration * 0.6);
+		return Timeline<ShapeSet> {
+			{ 0_cs, firstDuration, first },
+			{ firstDuration, duration, second }
+		};
+	};
+
+	// Returns a timeline with two shape sets, timed as a plosive
+	auto plosive = [&](ShapeSet first, ShapeSet second) {
+		centiseconds maxOcclusionDuration = 12_cs;
+		centiseconds leftOverlap = clamp(previousDuration / 2, 4_cs, maxOcclusionDuration);
+		centiseconds rightOverlap = min(duration, maxOcclusionDuration - leftOverlap);
+		return Timeline<ShapeSet> {
+			{ -leftOverlap, rightOverlap, first },
+			{ rightOverlap, duration, second }
+		};
+	};
+
+	if (!phone)				return single({ X });
+
+	switch (*phone) {
+	case Phone::AO:			return single({ E });
+	case Phone::AA:			return single({ D });
+	case Phone::IY:			return single({ B });
+	case Phone::UW:			return single({ F });
+	case Phone::EH:			return duration < 20_cs ? single({ C }) : single({ D });
+	case Phone::IH:			return single({ B });
+	case Phone::UH:			return single({ E });
+	case Phone::AH:			return single({ C });
+	case Phone::Schwa:		return single({ { B, C, D, E, F } });
+	case Phone::AE:			return single({ D });
+	case Phone::EY:			return duration < 20_cs ? diphthong({ C }, { B }) : diphthong({ D }, { B });
+	case Phone::AY:			return diphthong({ D }, { B });
+	case Phone::OW:			return diphthong({ E }, { F });
+	case Phone::AW:			return diphthong({ D }, { F });
+	case Phone::OY:			return diphthong({ F }, { B });
+	case Phone::ER:			return duration < 7_cs ? single({ B }) : single({ E });
+
+	case Phone::P:
+	case Phone::B:			return plosive({ A }, { A, B, C, D, E, F, G, H, X });
+	case Phone::T:
+	case Phone::D:
+	case Phone::K:			return single({ B, F });
+	case Phone::G:			return single({ B, C, E, F });
+	case Phone::CH:
+	case Phone::JH:			return single({ B, F });
+	case Phone::F:
+	case Phone::V:			return single({ G });
+	case Phone::TH:
+	case Phone::DH:
+	case Phone::S:
+	case Phone::Z:
+	case Phone::SH:
+	case Phone::ZH:			return single({ B, F });
+	case Phone::HH:			return single({ B, C, D, E, F });
+	case Phone::M:			return single({ A });
+	case Phone::N:			return single({ B, C, F });
+	case Phone::NG:			return single({ B, C, D, E, F });
+	case Phone::L:			return single({ E, F, H });
+	case Phone::R:			return single({ B, F });
+	case Phone::Y:			return single({ B });
+	case Phone::W:			return single({ F });
+
+	case Phone::Breath:
+	case Phone::Cough:
+	case Phone::Smack:		return single({ C });
+	case Phone::Noise:		return single({ B });
+
+	default:				throw std::invalid_argument("Unexpected phone.");
+	}
+}
diff --git a/src/animation/animationRules.h b/src/animation/animationRules.h
new file mode 100644
index 0000000..f6a9a2e
--- /dev/null
+++ b/src/animation/animationRules.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <set>
+#include <boost/optional.hpp>
+#include "Shape.h"
+#include "Timeline.h"
+#include "Phone.h"
+
+using ShapeSet = std::set<Shape>;
+
+Timeline<ShapeSet> animatePhone(boost::optional<Phone> phone, centiseconds duration, centiseconds previousDuration);