diff --git a/build.gradle.kts b/build.gradle.kts
index 87c3db6..59a0448 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -70,6 +70,7 @@ repositories {
 	maven("https://maven.fabricmc.net/")
 	maven("https://maven.minecraftforge.net/")
 	maven("https://maven.neoforged.net/releases/")
+	maven("https://maven.wispforest.io/releases/") { name = "Wisp Forest (owo-lib)" }
 }
 
 val loaderVersion: String by project
@@ -90,6 +91,10 @@ dependencies {
 
 			modImplementation("net.fabricmc:fabric-loader:${loaderVersion}")
 			modImplementation("net.fabricmc.fabric-api:fabric-api:${fabricApiVersion}")
+
+			// owo-lib for GUI
+			modImplementation("io.wispforest:owo-lib:0.12.15+1.21")
+			include("io.wispforest:owo-sentinel:0.12.15+1.21")
 		}
 
 		"neoforge" -> {
diff --git a/src/main/kotlin/com/bnair/roadrunner/RoadRunner.kt b/src/main/kotlin/com/bnair/roadrunner/RoadRunner.kt
index 1bd6250..2e51950 100644
--- a/src/main/kotlin/com/bnair/roadrunner/RoadRunner.kt
+++ b/src/main/kotlin/com/bnair/roadrunner/RoadRunner.kt
@@ -1,5 +1,7 @@
 package com.bnair.roadrunner
 
+import com.bnair.roadrunner.registry.ModItems
+
 //? if fabric {
 import net.fabricmc.api.ModInitializer
 //?}
@@ -11,6 +13,7 @@ internal const val MOD_ID = "roadrunner"
 
 internal fun initializeMod() {
     println("RoadRunner Mod has been initialized.")
+    ModItems.init()
 }
 
 //? if fabric {
diff --git a/src/main/kotlin/com/bnair/roadrunner/client/RoadRunnerClient.kt b/src/main/kotlin/com/bnair/roadrunner/client/RoadRunnerClient.kt
new file mode 100644
index 0000000..7f49530
--- /dev/null
+++ b/src/main/kotlin/com/bnair/roadrunner/client/RoadRunnerClient.kt
@@ -0,0 +1,30 @@
+package com.bnair.roadrunner.client
+
+import com.bnair.roadrunner.MOD_ID
+import com.bnair.roadrunner.client.gui.RoadPlannerScreen
+import com.bnair.roadrunner.registry.ModItems
+import net.minecraft.client.Minecraft
+
+//? if fabric {
+import net.fabricmc.api.ClientModInitializer
+import net.fabricmc.fabric.api.event.player.UseItemCallback
+import net.minecraft.world.InteractionResultHolder
+//?}
+
+//? if fabric {
+class RoadRunnerClient : ClientModInitializer {
+    override fun onInitializeClient() {
+        println("$MOD_ID client initialized")
+
+        UseItemCallback.EVENT.register { player, world, hand ->
+            val stack = player.getItemInHand(hand)
+            if (stack.item == ModItems.ROAD_PLANNER && world.isClientSide) {
+                Minecraft.getInstance().setScreen(RoadPlannerScreen())
+                InteractionResultHolder.success(stack)
+            } else {
+                InteractionResultHolder.pass(stack)
+            }
+        }
+    }
+}
+//?}
diff --git a/src/main/kotlin/com/bnair/roadrunner/client/gui/RoadPlannerScreen.kt b/src/main/kotlin/com/bnair/roadrunner/client/gui/RoadPlannerScreen.kt
new file mode 100644
index 0000000..74e972d
--- /dev/null
+++ b/src/main/kotlin/com/bnair/roadrunner/client/gui/RoadPlannerScreen.kt
@@ -0,0 +1,414 @@
+package com.bnair.roadrunner.client.gui
+
+import com.bnair.roadrunner.math.BezierCurve
+import com.bnair.roadrunner.math.Vec3d
+import com.bnair.roadrunner.road.RoadNetwork
+import com.bnair.roadrunner.road.RoadProfile
+import com.bnair.roadrunner.road.RoadSegment
+import com.mojang.blaze3d.systems.RenderSystem
+import net.minecraft.client.Minecraft
+import net.minecraft.client.gui.GuiGraphics
+import net.minecraft.client.gui.screens.Screen
+import net.minecraft.network.chat.Component
+import org.lwjgl.glfw.GLFW
+import kotlin.math.floor
+
+enum class DrawingTool {
+    SELECT,
+    STRAIGHT,
+    CURVE
+}
+
+class RoadPlannerScreen : Screen(Component.literal("Road Planner")) {
+    private var currentTool = DrawingTool.STRAIGHT
+    private var currentProfile = RoadProfile.highway()
+
+    private var mapCenterX = 0.0
+    private var mapCenterZ = 0.0
+    private var mapScale = 2.0
+
+    private val plannedSegments = mutableListOf<PlannedSegment>()
+    private var currentSegment: PlannedSegment? = null
+
+    private var isDragging = false
+    private var lastMouseX = 0.0
+    private var lastMouseY = 0.0
+
+    private val toolbarHeight = 40
+    private val sidebarWidth = 150
+
+    data class PlannedSegment(
+        val points: MutableList<ScreenPoint> = mutableListOf(),
+        var profile: RoadProfile = RoadProfile.highway(),
+        var isComplete: Boolean = false
+    )
+
+    data class ScreenPoint(var screenX: Double, var screenY: Double)
+
+    override fun init() {
+        super.init()
+        val player = Minecraft.getInstance().player ?: return
+        mapCenterX = player.x
+        mapCenterZ = player.z
+    }
+
+    override fun render(graphics: GuiGraphics, mouseX: Int, mouseY: Int, partialTick: Float) {
+        renderBackground(graphics, mouseX, mouseY, partialTick)
+
+        renderMap(graphics, mouseX, mouseY)
+        renderToolbar(graphics, mouseX, mouseY)
+        renderSidebar(graphics, mouseX, mouseY)
+        renderCurrentDrawing(graphics, mouseX, mouseY)
+        renderPlannedSegments(graphics)
+
+        super.render(graphics, mouseX, mouseY, partialTick)
+    }
+
+    private fun renderMap(graphics: GuiGraphics, mouseX: Int, mouseY: Int) {
+        val mapLeft = sidebarWidth
+        val mapTop = toolbarHeight
+        val mapWidth = width - sidebarWidth
+        val mapHeight = height - toolbarHeight
+
+        graphics.fill(mapLeft, mapTop, width, height, 0xFF1a1a2e.toInt())
+
+        renderGrid(graphics, mapLeft, mapTop, mapWidth, mapHeight)
+
+        val playerScreenX = worldToScreenX(mapCenterX, mapLeft, mapWidth)
+        val playerScreenY = worldToScreenZ(mapCenterZ, mapTop, mapHeight)
+        graphics.fill(
+            playerScreenX.toInt() - 3,
+            playerScreenY.toInt() - 3,
+            playerScreenX.toInt() + 3,
+            playerScreenY.toInt() + 3,
+            0xFF00FF00.toInt()
+        )
+
+        val worldX = screenToWorldX(mouseX.toDouble(), mapLeft, mapWidth)
+        val worldZ = screenToWorldZ(mouseY.toDouble(), mapTop, mapHeight)
+        graphics.drawString(
+            font,
+            "X: ${floor(worldX).toInt()}, Z: ${floor(worldZ).toInt()}",
+            mapLeft + 5,
+            height - 15,
+            0xFFFFFF
+        )
+    }
+
+    private fun renderGrid(graphics: GuiGraphics, mapLeft: Int, mapTop: Int, mapWidth: Int, mapHeight: Int) {
+        val gridSpacing = 16.0 * mapScale
+
+        val startWorldX = screenToWorldX(mapLeft.toDouble(), mapLeft, mapWidth)
+        val endWorldX = screenToWorldX((mapLeft + mapWidth).toDouble(), mapLeft, mapWidth)
+        val startWorldZ = screenToWorldZ(mapTop.toDouble(), mapTop, mapHeight)
+        val endWorldZ = screenToWorldZ((mapTop + mapHeight).toDouble(), mapTop, mapHeight)
+
+        val gridStartX = floor(startWorldX / 16) * 16
+        val gridStartZ = floor(startWorldZ / 16) * 16
+
+        var x = gridStartX
+        while (x <= endWorldX) {
+            val screenX = worldToScreenX(x, mapLeft, mapWidth).toInt()
+            if (screenX in mapLeft until (mapLeft + mapWidth)) {
+                val color = if (x.toInt() % 64 == 0) 0x40FFFFFF else 0x20FFFFFF
+                graphics.fill(screenX, mapTop, screenX + 1, mapTop + mapHeight, color)
+            }
+            x += 16
+        }
+
+        var z = gridStartZ
+        while (z <= endWorldZ) {
+            val screenY = worldToScreenZ(z, mapTop, mapHeight).toInt()
+            if (screenY in mapTop until (mapTop + mapHeight)) {
+                val color = if (z.toInt() % 64 == 0) 0x40FFFFFF else 0x20FFFFFF
+                graphics.fill(mapLeft, screenY, mapLeft + mapWidth, screenY + 1, color)
+            }
+            z += 16
+        }
+    }
+
+    private fun renderToolbar(graphics: GuiGraphics, mouseX: Int, mouseY: Int) {
+        graphics.fill(0, 0, width, toolbarHeight, 0xFF2d2d44.toInt())
+
+        val tools = listOf(
+            Triple(DrawingTool.SELECT, "Select", 10),
+            Triple(DrawingTool.STRAIGHT, "Straight", 80),
+            Triple(DrawingTool.CURVE, "Curve", 160)
+        )
+
+        tools.forEach { (tool, name, x) ->
+            val isSelected = currentTool == tool
+            val bgColor = if (isSelected) 0xFF4a4a6a.toInt() else 0xFF3a3a5a.toInt()
+            val isHovered = mouseX in x until (x + 60) && mouseY in 5 until 35
+
+            graphics.fill(x, 5, x + 60, 35, if (isHovered) 0xFF5a5a7a.toInt() else bgColor)
+            graphics.drawCenteredString(font, name, x + 30, 15, 0xFFFFFF)
+        }
+
+        graphics.drawString(font, "Scroll to zoom | Drag to pan", 250, 15, 0xAAAAAA)
+    }
+
+    private fun renderSidebar(graphics: GuiGraphics, mouseX: Int, mouseY: Int) {
+        graphics.fill(0, toolbarHeight, sidebarWidth, height, 0xFF252538.toInt())
+
+        graphics.drawString(font, "Road Profile", 10, toolbarHeight + 10, 0xFFFFFF)
+
+        val profiles = listOf(
+            "Simple" to RoadProfile.singleLaneEachWay(),
+            "Highway 2L" to RoadProfile.highway(2),
+            "Highway 3L" to RoadProfile.highway(3),
+            "With Transit" to RoadProfile.withPublicTransport()
+        )
+
+        profiles.forEachIndexed { index, (name, profile) ->
+            val y = toolbarHeight + 30 + index * 25
+            val isSelected = currentProfile.totalWidth == profile.totalWidth
+            val bgColor = if (isSelected) 0xFF4a4a6a.toInt() else 0xFF3a3a5a.toInt()
+            val isHovered = mouseX in 5 until (sidebarWidth - 5) && mouseY in y until (y + 20)
+
+            graphics.fill(5, y, sidebarWidth - 5, y + 20, if (isHovered) 0xFF5a5a7a.toInt() else bgColor)
+            graphics.drawString(font, name, 10, y + 6, 0xFFFFFF)
+        }
+
+        graphics.drawString(font, "Segments: ${plannedSegments.size}", 10, height - 60, 0xAAAAAA)
+
+        val buildButtonY = height - 35
+        val isHovered = mouseX in 10 until (sidebarWidth - 10) && mouseY in buildButtonY until (buildButtonY + 25)
+        graphics.fill(10, buildButtonY, sidebarWidth - 10, buildButtonY + 25, 
+            if (isHovered) 0xFF22AA22.toInt() else 0xFF118811.toInt())
+        graphics.drawCenteredString(font, "BUILD", sidebarWidth / 2, buildButtonY + 8, 0xFFFFFF)
+    }
+
+    private fun renderCurrentDrawing(graphics: GuiGraphics, mouseX: Int, mouseY: Int) {
+        val segment = currentSegment ?: return
+
+        segment.points.forEach { point ->
+            graphics.fill(
+                point.screenX.toInt() - 4,
+                point.screenY.toInt() - 4,
+                point.screenX.toInt() + 4,
+                point.screenY.toInt() + 4,
+                0xFFFF6600.toInt()
+            )
+        }
+
+        if (segment.points.isNotEmpty()) {
+            val lastPoint = segment.points.last()
+            graphics.fill(
+                lastPoint.screenX.toInt(),
+                lastPoint.screenY.toInt(),
+                mouseX,
+                mouseY,
+                0x80FF6600.toInt()
+            )
+        }
+    }
+
+    private fun renderPlannedSegments(graphics: GuiGraphics) {
+        val mapLeft = sidebarWidth
+        val mapTop = toolbarHeight
+        val mapWidth = width - sidebarWidth
+        val mapHeight = height - toolbarHeight
+
+        plannedSegments.forEach { segment ->
+            if (segment.points.size >= 2) {
+                val curve = createCurveFromPoints(segment.points, mapLeft, mapTop, mapWidth, mapHeight)
+                val samples = curve.sample(50)
+
+                for (i in 0 until samples.size - 1) {
+                    val p1 = samples[i]
+                    val p2 = samples[i + 1]
+
+                    val sx1 = worldToScreenX(p1.x, mapLeft, mapWidth).toInt()
+                    val sy1 = worldToScreenZ(p1.z, mapTop, mapHeight).toInt()
+                    val sx2 = worldToScreenX(p2.x, mapLeft, mapWidth).toInt()
+                    val sy2 = worldToScreenZ(p2.z, mapTop, mapHeight).toInt()
+
+                    drawLine(graphics, sx1, sy1, sx2, sy2, 0xFF4488FF.toInt(), segment.profile.totalWidth.toInt() / 2)
+                }
+            }
+        }
+    }
+
+    private fun drawLine(graphics: GuiGraphics, x1: Int, y1: Int, x2: Int, y2: Int, color: Int, thickness: Int = 2) {
+        val dx = x2 - x1
+        val dy = y2 - y1
+        val steps = maxOf(kotlin.math.abs(dx), kotlin.math.abs(dy), 1)
+
+        for (i in 0..steps) {
+            val t = i.toFloat() / steps
+            val x = (x1 + dx * t).toInt()
+            val y = (y1 + dy * t).toInt()
+            graphics.fill(x - thickness, y - thickness, x + thickness, y + thickness, color)
+        }
+    }
+
+    override fun mouseClicked(mouseX: Double, mouseY: Double, button: Int): Boolean {
+        if (button == GLFW.GLFW_MOUSE_BUTTON_LEFT) {
+            if (mouseY < toolbarHeight) {
+                handleToolbarClick(mouseX.toInt(), mouseY.toInt())
+                return true
+            }
+
+            if (mouseX < sidebarWidth) {
+                handleSidebarClick(mouseX.toInt(), mouseY.toInt())
+                return true
+            }
+
+            if (currentTool == DrawingTool.STRAIGHT || currentTool == DrawingTool.CURVE) {
+                if (currentSegment == null) {
+                    currentSegment = PlannedSegment(profile = currentProfile)
+                }
+                currentSegment?.points?.add(ScreenPoint(mouseX, mouseY))
+                return true
+            }
+        }
+
+        if (button == GLFW.GLFW_MOUSE_BUTTON_RIGHT) {
+            currentSegment?.let { segment ->
+                if (segment.points.size >= 2) {
+                    segment.isComplete = true
+                    plannedSegments.add(segment)
+                }
+                currentSegment = null
+            }
+            return true
+        }
+
+        if (button == GLFW.GLFW_MOUSE_BUTTON_MIDDLE) {
+            isDragging = true
+            lastMouseX = mouseX
+            lastMouseY = mouseY
+            return true
+        }
+
+        return super.mouseClicked(mouseX, mouseY, button)
+    }
+
+    override fun mouseReleased(mouseX: Double, mouseY: Double, button: Int): Boolean {
+        if (button == GLFW.GLFW_MOUSE_BUTTON_MIDDLE) {
+            isDragging = false
+            return true
+        }
+        return super.mouseReleased(mouseX, mouseY, button)
+    }
+
+    override fun mouseDragged(mouseX: Double, mouseY: Double, button: Int, dragX: Double, dragY: Double): Boolean {
+        if (isDragging) {
+            mapCenterX -= dragX * mapScale
+            mapCenterZ -= dragY * mapScale
+            return true
+        }
+        return super.mouseDragged(mouseX, mouseY, button, dragX, dragY)
+    }
+
+    override fun mouseScrolled(mouseX: Double, mouseY: Double, horizontalAmount: Double, verticalAmount: Double): Boolean {
+        val zoomFactor = if (verticalAmount > 0) 0.8 else 1.25
+        mapScale = (mapScale * zoomFactor).coerceIn(0.5, 20.0)
+        return true
+    }
+
+    private fun handleToolbarClick(mouseX: Int, mouseY: Int) {
+        when {
+            mouseX in 10 until 70 -> currentTool = DrawingTool.SELECT
+            mouseX in 80 until 140 -> currentTool = DrawingTool.STRAIGHT
+            mouseX in 160 until 220 -> currentTool = DrawingTool.CURVE
+        }
+    }
+
+    private fun handleSidebarClick(mouseX: Int, mouseY: Int) {
+        val profiles = listOf(
+            RoadProfile.singleLaneEachWay(),
+            RoadProfile.highway(2),
+            RoadProfile.highway(3),
+            RoadProfile.withPublicTransport()
+        )
+
+        profiles.forEachIndexed { index, profile ->
+            val y = toolbarHeight + 30 + index * 25
+            if (mouseY in y until (y + 20)) {
+                currentProfile = profile
+                return
+            }
+        }
+
+        val buildButtonY = height - 35
+        if (mouseY in buildButtonY until (buildButtonY + 25)) {
+            buildRoads()
+        }
+    }
+
+    private fun buildRoads() {
+        val mapLeft = sidebarWidth
+        val mapTop = toolbarHeight
+        val mapWidth = width - sidebarWidth
+        val mapHeight = height - toolbarHeight
+
+        val network = RoadNetwork()
+
+        plannedSegments.forEach { segment ->
+            if (segment.points.size >= 2) {
+                val curve = createCurveFromPoints(segment.points, mapLeft, mapTop, mapWidth, mapHeight)
+                network.addSegment(RoadSegment(curve, segment.profile))
+            }
+        }
+
+        val blocks = network.getAllBlocks()
+        val costs = network.estimateMaterialCost()
+
+        println("Road network planned:")
+        println("  Total blocks: ${blocks.size}")
+        println("  Materials needed:")
+        costs.forEach { (material, count) ->
+            println("    $material: $count")
+        }
+
+        Minecraft.getInstance().player?.sendSystemMessage(
+            Component.literal("Planned ${plannedSegments.size} road segments (${blocks.size} blocks)")
+        )
+    }
+
+    private fun createCurveFromPoints(points: List<ScreenPoint>, mapLeft: Int, mapTop: Int, mapWidth: Int, mapHeight: Int): BezierCurve {
+        val worldPoints = points.map { point ->
+            Vec3d(
+                screenToWorldX(point.screenX, mapLeft, mapWidth),
+                64.0,
+                screenToWorldZ(point.screenY, mapTop, mapHeight)
+            )
+        }
+
+        return when {
+            worldPoints.size == 2 -> BezierCurve.line(worldPoints[0], worldPoints[1])
+            worldPoints.size >= 4 -> BezierCurve(
+                worldPoints[0],
+                worldPoints[1],
+                worldPoints[worldPoints.size - 2],
+                worldPoints.last()
+            )
+            else -> {
+                val p0 = worldPoints[0]
+                val p3 = worldPoints.last()
+                val mid = if (worldPoints.size > 2) worldPoints[1] else (p0 + p3) / 2.0
+                BezierCurve(p0, mid, mid, p3)
+            }
+        }
+    }
+
+    private fun worldToScreenX(worldX: Double, mapLeft: Int, mapWidth: Int): Double {
+        return mapLeft + mapWidth / 2.0 + (worldX - mapCenterX) / mapScale
+    }
+
+    private fun worldToScreenZ(worldZ: Double, mapTop: Int, mapHeight: Int): Double {
+        return mapTop + mapHeight / 2.0 + (worldZ - mapCenterZ) / mapScale
+    }
+
+    private fun screenToWorldX(screenX: Double, mapLeft: Int, mapWidth: Int): Double {
+        return mapCenterX + (screenX - mapLeft - mapWidth / 2.0) * mapScale
+    }
+
+    private fun screenToWorldZ(screenY: Double, mapTop: Int, mapHeight: Int): Double {
+        return mapCenterZ + (screenY - mapTop - mapHeight / 2.0) * mapScale
+    }
+
+    override fun isPauseScreen() = false
+}
diff --git a/src/main/kotlin/com/bnair/roadrunner/registry/ModItems.kt b/src/main/kotlin/com/bnair/roadrunner/registry/ModItems.kt
new file mode 100644
index 0000000..46434bc
--- /dev/null
+++ b/src/main/kotlin/com/bnair/roadrunner/registry/ModItems.kt
@@ -0,0 +1,39 @@
+package com.bnair.roadrunner.registry
+
+import com.bnair.roadrunner.MOD_ID
+import net.minecraft.core.Registry
+import net.minecraft.core.registries.BuiltInRegistries
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.world.item.CreativeModeTabs
+import net.minecraft.world.item.Item
+
+//? if fabric {
+import net.fabricmc.fabric.api.itemgroup.v1.ItemGroupEvents
+//?}
+
+object ModItems {
+    private val ITEMS = mutableMapOf<String, Item>()
+
+    val ROAD_PLANNER: Item = register("road_planner", Item(Item.Properties().stacksTo(1)))
+
+    private fun register(name: String, item: Item): Item {
+        ITEMS[name] = item
+        return item
+    }
+
+    fun init() {
+        //? if fabric {
+        ITEMS.forEach { (name, item) ->
+            Registry.register(
+                BuiltInRegistries.ITEM,
+                ResourceLocation.fromNamespaceAndPath(MOD_ID, name),
+                item
+            )
+        }
+
+        ItemGroupEvents.modifyEntriesEvent(CreativeModeTabs.TOOLS_AND_UTILITIES).register { content ->
+            content.accept(ROAD_PLANNER)
+        }
+        //?}
+    }
+}
diff --git a/src/main/resources/fabric.mod.json b/src/main/resources/fabric.mod.json
index 404661c..1bf665d 100644
--- a/src/main/resources/fabric.mod.json
+++ b/src/main/resources/fabric.mod.json
@@ -15,6 +15,9 @@
 	"entrypoints": {
 		"main": [
 			"com.bnair.roadrunner.RoadRunnerFabric"
+		],
+		"client": [
+			"com.bnair.roadrunner.client.RoadRunnerClient"
 		]
 	},
 	"mixins": [
@@ -23,7 +26,8 @@
 	"depends": {
 		"fabric": ">=${loader_version}",
 		"fabric-api": "*",
-		"minecraft": "${minecraft_version}"
+		"minecraft": "${minecraft_version}",
+		"owo-lib": "*"
 	},
 	"custom": {
 		"modmenu": {