diff --git a/src/commonMain/kotlin/baaahs/gl/glsl/GlslType.kt b/src/commonMain/kotlin/baaahs/gl/glsl/GlslType.kt
index c2488e3f0a..085882ef2a 100644
--- a/src/commonMain/kotlin/baaahs/gl/glsl/GlslType.kt
+++ b/src/commonMain/kotlin/baaahs/gl/glsl/GlslType.kt
@@ -14,7 +14,39 @@ sealed class GlslType constructor(
 
     val mutableDefaultInitializer: MutablePort get() = MutableConstPort(defaultInitializer.s, this)
 
+    fun arrayOf(count: kotlin.Int): Array = Array(this, count)
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is GlslType) return false
+
+        if (glslLiteral != other.glslLiteral) return false
+
+        return true
+    }
+
+    override fun hashCode(): kotlin.Int {
+        return glslLiteral.hashCode()
+    }
+
+    override fun toString(): String {
+        return "GlslType($glslLiteral)"
+    }
+
+    object Bool : GlslType("bool", GlslExpr("false"))
+    object Float : GlslType("float", GlslExpr("0."))
+    object Matrix4 : GlslType("mat4")
+    object Vec2 : GlslType("vec2")
+    object Vec3 : GlslType("vec3")
+    object Vec4 : GlslType("vec4")
+    object Int : GlslType("int", GlslExpr("0"))
+    object Sampler2D : GlslType("sampler2D")
+    object Void : GlslType("void")
+
     private class OtherGlslType(glslLiteral: String) : GlslType(glslLiteral)
+
+    class Array(val type: GlslType, length: kotlin.Int) : GlslType("${type.glslLiteral}[$length]")
+
     class Struct(
         val name: String,
         val fields: Map<String, GlslType>,
@@ -81,33 +113,6 @@ sealed class GlslType constructor(
         }
     }
 
-    object Bool : GlslType("bool", GlslExpr("false"))
-    object Float : GlslType("float", GlslExpr("0."))
-    object Matrix4 : GlslType("mat4")
-    object Vec2 : GlslType("vec2")
-    object Vec3 : GlslType("vec3")
-    object Vec4 : GlslType("vec4")
-    object Int : GlslType("int", GlslExpr("0"))
-    object Sampler2D : GlslType("sampler2D")
-    object Void : GlslType("void")
-
-    override fun equals(other: Any?): Boolean {
-        if (this === other) return true
-        if (other !is GlslType) return false
-
-        if (glslLiteral != other.glslLiteral) return false
-
-        return true
-    }
-
-    override fun hashCode(): kotlin.Int {
-        return glslLiteral.hashCode()
-    }
-
-    override fun toString(): String {
-        return "GlslType($glslLiteral)"
-    }
-
     companion object {
         val types = mutableMapOf<String, GlslType>()
 
diff --git a/src/commonTest/kotlin/baaahs/gl/glsl/GlslTypeSpec.kt b/src/commonTest/kotlin/baaahs/gl/glsl/GlslTypeSpec.kt
new file mode 100644
index 0000000000..3213ec3278
--- /dev/null
+++ b/src/commonTest/kotlin/baaahs/gl/glsl/GlslTypeSpec.kt
@@ -0,0 +1,75 @@
+package baaahs.gl.glsl
+
+import baaahs.describe
+import baaahs.gl.override
+import baaahs.toBeSpecified
+import baaahs.toEqual
+import ch.tutteli.atrium.api.verbs.expect
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.dsl.Skip
+
+object GlslTypeSpec : Spek({
+    describe<GlslType> {
+        val type by value<GlslType> { toBeSpecified() }
+
+        describe("arrays") {
+            override(type) { GlslType.Int.arrayOf(8) }
+
+            it("has valid a GLSL declaration") {
+                expect(type.glslLiteral)
+                    .toEqual("int[8]")
+            }
+        }
+
+        describe("structs") {
+            override(type) {
+                GlslType.Struct(
+                    "FixtureInfo",
+                    "origin" to GlslType.Vec3,
+                    "heading" to GlslType.Vec3,
+                    "matrix" to GlslType.Matrix4
+                )
+            }
+
+            it("#toGlsl generates valid a GLSL declaration") {
+                expect((type as GlslType.Struct).toGlsl(GlslCode.Namespace("pfx"), emptySet()))
+                    .toEqual(
+                        """
+                        struct pfx_FixtureInfo {
+                            vec3 origin;
+                            vec3 heading;
+                            mat4 matrix;
+                        };
+                    """.trimIndent() + "\n\n"
+                    )
+            }
+
+            context("with arrays") {
+                override(type) {
+                    GlslType.Struct(
+                        "FixtureInfo",
+                        "origin" to GlslType.Vec3.arrayOf(3),
+                        "heading" to GlslType.Vec3,
+                        "matrix" to GlslType.Matrix4
+                    )
+                }
+
+                it(
+                    "#toGlsl generates valid a GLSL declaration",
+                    skip = Skip.Yes("Fix position of array marker in declaration.")
+                ) {
+                    expect((type as GlslType.Struct).toGlsl(GlslCode.Namespace("pfx"), emptySet()))
+                        .toEqual(
+                            """
+                            struct pfx_FixtureInfo {
+                                vec3 origin[3];
+                                vec3 heading;
+                                mat4 matrix;
+                            };
+                        """.trimIndent() + "\n\n"
+                        )
+                }
+            }
+        }
+    }
+})