diff --git a/gradle.properties b/gradle.properties
index 943936d002..0677f5394d 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -19,4 +19,4 @@ kotlin.code.style=official
 	loom_version=0.5-SNAPSHOT
 # Kotlin
 	kotlin_version=1.4.0
-	fabric_kotlin_version=1.4.0+build.1
\ No newline at end of file
+	fabric_kotlin_version=1.4.21+build.1
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/Components.kt b/src/main/kotlin/li/cli/oc/Components.kt
index dc8d6cd0d8..60bc5601d3 100644
--- a/src/main/kotlin/li/cli/oc/Components.kt
+++ b/src/main/kotlin/li/cli/oc/Components.kt
@@ -2,12 +2,16 @@ package li.cli.oc
 
 import li.cli.oc.blocks.*
 import li.cli.oc.components.BlockEntitiesComponent
+import li.cli.oc.client.gui.blocks.CaseScreen
+import li.cli.oc.client.gui.blocks.CaseScreenHandler
 import li.cli.oc.items.Analyzer
 import li.cli.oc.items.Debugger
 import li.cli.oc.items.commons.ComponentBlockItem
 import li.cli.oc.items.commons.ComponentItem
 import net.minecraft.block.Block
 import net.minecraft.item.Item
+import net.fabricmc.fabric.api.screenhandler.v1.ScreenHandlerRegistry
+import net.minecraft.screen.ScreenHandlerType
 import net.minecraft.util.Identifier
 import net.minecraft.util.registry.Registry
 
@@ -178,4 +182,7 @@ object Components {
             Registry.register(Registry.ITEM, Identifier(OpenComputers.modId, x.id), x.item)
         }
     }
+
+    val CASE1 = Case(1)
+    val CASE_SCREEN_HANDLER: ScreenHandlerType<CaseScreenHandler> = ScreenHandlerRegistry.registerExtended(Identifier(OpenComputers.modId), ::CaseScreenHandler)
 }
diff --git a/src/main/kotlin/li/cli/oc/blockentity/Case.kt b/src/main/kotlin/li/cli/oc/blockentity/Case.kt
index 1ad4dfee15..b6b9fe4981 100644
--- a/src/main/kotlin/li/cli/oc/blockentity/Case.kt
+++ b/src/main/kotlin/li/cli/oc/blockentity/Case.kt
@@ -1,6 +1,43 @@
 package li.cli.oc.blockentity
 
 import li.cli.oc.blocks.commons.RedstoneAwareEntity
+import li.cli.oc.client.gui.blocks.CaseScreenHandler
 import li.cli.oc.components.BlockEntitiesComponent
+import net.fabricmc.fabric.api.screenhandler.v1.ExtendedScreenHandlerFactory
+import net.minecraft.block.BlockState
+import net.minecraft.entity.player.PlayerEntity
+import net.minecraft.entity.player.PlayerInventory
+import net.minecraft.nbt.CompoundTag
+import net.minecraft.network.PacketByteBuf
+import net.minecraft.screen.ScreenHandler
+import net.minecraft.server.network.ServerPlayerEntity
+import net.minecraft.text.Text
 
-class CaseEntity : RedstoneAwareEntity(BlockEntitiesComponent.Case)
\ No newline at end of file
+class CaseEntity(var Tier: Int) : RedstoneAwareEntity(BlockEntitiesComponent.Case), ExtendedScreenHandlerFactory {
+    init {
+        markDirty()
+    }
+
+    override fun createMenu(syncId: Int, inv: PlayerInventory, player: PlayerEntity): ScreenHandler {
+        return CaseScreenHandler(syncId, inv, Tier)
+    }
+
+    override fun getDisplayName(): Text {
+        return Text.of("Computer")
+    }
+
+    override fun writeScreenOpeningData(playerEntity: ServerPlayerEntity?, buf: PacketByteBuf?) {
+        buf?.writeInt(Tier)
+    }
+
+    override fun toTag(tag: CompoundTag): CompoundTag {
+        super.toTag(tag)
+        tag.putInt("tier", Tier)
+        return tag
+    }
+
+    override fun fromTag(state: BlockState?, tag: CompoundTag?) {
+        super.fromTag(state, tag)
+        Tier = tag?.getInt("tier")!!
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/blocks/Case.kt b/src/main/kotlin/li/cli/oc/blocks/Case.kt
index b93bb2fb4c..c249f4aa73 100644
--- a/src/main/kotlin/li/cli/oc/blocks/Case.kt
+++ b/src/main/kotlin/li/cli/oc/blocks/Case.kt
@@ -1,4 +1,4 @@
-package li.cli.oc.blocks
+package li.cli.oc.blocks;
 
 import li.cli.oc.blockentity.CaseEntity
 import li.cli.oc.blocks.commons.TecBlock
@@ -6,11 +6,17 @@ import li.cli.oc.render.Color
 import net.fabricmc.fabric.api.`object`.builder.v1.block.FabricBlockSettings
 import net.minecraft.block.*
 import net.minecraft.block.entity.BlockEntity
+import net.minecraft.entity.player.PlayerEntity
 import net.minecraft.item.ItemPlacementContext
 import net.minecraft.state.StateManager
 import net.minecraft.state.property.BooleanProperty
+import net.minecraft.util.ActionResult
+import net.minecraft.util.Hand
+import net.minecraft.util.hit.BlockHitResult
+import net.minecraft.util.math.BlockPos
 import net.minecraft.util.math.Direction
 import net.minecraft.world.BlockView
+import net.minecraft.world.World
 
 class Case(var Tier: Int) : TecBlock(FabricBlockSettings.of(Material.METAL)) {
 
@@ -35,11 +41,22 @@ class Case(var Tier: Int) : TecBlock(FabricBlockSettings.of(Material.METAL)) {
         return this.defaultState.with(facing, ctx?.playerFacing?.opposite)
     }
 
-    override fun createBlockEntity(world: BlockView?): BlockEntity {
-        return CaseEntity()
+    override fun createBlockEntity(world: BlockView?): BlockEntity? {
+        return CaseEntity(Tier);
     }
 
     override fun getRenderType(state: BlockState?): BlockRenderType {
-        return BlockRenderType.MODEL
+        return BlockRenderType.MODEL;
+    }
+
+    override fun onUse(state: BlockState, world: World, pos: BlockPos?, player: PlayerEntity, hand: Hand?, hit: BlockHitResult?): ActionResult? {
+        // Open the case screen if we can
+        if (!world.isClient) {
+            val screenHandlerFactory = state.createScreenHandlerFactory(world, pos)
+            if (screenHandlerFactory != null) {
+                player.openHandledScreen(screenHandlerFactory)
+            }
+        }
+        return ActionResult.SUCCESS
     }
 }
diff --git a/src/main/kotlin/li/cli/oc/client/ClientInit.kt b/src/main/kotlin/li/cli/oc/client/ClientInit.kt
index 0f5ce4d818..d1bbc2e1f7 100644
--- a/src/main/kotlin/li/cli/oc/client/ClientInit.kt
+++ b/src/main/kotlin/li/cli/oc/client/ClientInit.kt
@@ -4,14 +4,16 @@ import li.cli.oc.Components
 import li.cli.oc.OpenComputers
 import li.cli.oc.blocks.Case
 import li.cli.oc.blocks.Screen
+import li.cli.oc.client.gui.blocks.CaseScreen
 import li.cli.oc.items.commons.ComponentBlockItem
 import li.cli.oc.render.BaseModelProvider
-import li.cli.oc.render.block.CableModel
 import li.cli.oc.render.block.ScreenModel
+import li.cli.oc.render.block.CableModel
 import net.fabricmc.api.ClientModInitializer
 import net.fabricmc.fabric.api.blockrenderlayer.v1.BlockRenderLayerMap
 import net.fabricmc.fabric.api.client.model.ModelLoadingRegistry
 import net.fabricmc.fabric.api.client.rendering.v1.ColorProviderRegistry
+import net.fabricmc.fabric.api.client.screenhandler.v1.ScreenRegistry
 import net.minecraft.block.BlockState
 import net.minecraft.client.render.RenderLayer
 import net.minecraft.item.ItemStack
@@ -25,6 +27,7 @@ object ClientInit : ClientModInitializer {
         ModelLoadingRegistry.INSTANCE.registerResourceProvider { BaseModelProvider(Identifier(OpenComputers.modId, "block/cable"), CableModel()) }
         ModelLoadingRegistry.INSTANCE.registerResourceProvider { BaseModelProvider(Identifier(OpenComputers.modId, "block/screen"), ScreenModel()) }
 
+
         ColorProviderRegistry.BLOCK.register(handleBlockColor,
             Components.Blocks.CaseOne.block,
             Components.Blocks.CaseTwo.block,
@@ -46,6 +49,8 @@ object ClientInit : ClientModInitializer {
         )
 
         BlockRenderLayerMap.INSTANCE.putBlock(Components.Blocks.Assembler.block, RenderLayer.getTranslucent());
+
+        ScreenRegistry.register(Components.CASE_SCREEN_HANDLER, ::CaseScreen)
     }
 
     private  val handleItemColor = fun (item: ItemStack, tintIndex: Int): Int {
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreen.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreen.kt
new file mode 100644
index 0000000000..6f47651cc6
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreen.kt
@@ -0,0 +1,97 @@
+package li.cli.oc.client.gui.blocks
+
+import com.mojang.blaze3d.systems.RenderSystem
+import li.cli.oc.OpenComputers
+import net.minecraft.client.gui.screen.ingame.HandledScreen
+import net.minecraft.client.gui.widget.TexturedButtonWidget
+import net.minecraft.client.util.math.MatrixStack
+import net.minecraft.entity.player.PlayerInventory
+import net.minecraft.screen.ScreenHandler
+import net.minecraft.text.Text
+import net.minecraft.util.Identifier
+
+class CaseScreen(handler: ScreenHandler?, inventory: PlayerInventory?, title: Text?) : HandledScreen<ScreenHandler?>(
+    handler,
+    inventory,
+    title
+) {
+
+    override fun drawBackground(matrices: MatrixStack?, delta: Float, mouseX: Int, mouseY: Int) {
+        RenderSystem.color4f(1.0f, 1.0f, 1.0f, 1.0f)
+        assert(client != null)
+        client!!.textureManager.bindTexture(TEXTURE)
+        val x = (width - backgroundWidth) / 2
+        val y = (height - backgroundHeight) / 2
+        drawTexture(matrices, x, y, 0, 0, backgroundWidth, backgroundHeight)
+
+        client!!.textureManager.bindTexture(COMP_TEXTURE)
+        drawTexture(matrices, x, y + 1, 0, 0, 256, 256)
+
+        client!!.textureManager.bindTexture(SLOT_TEXTURE)
+        val tier = (handler as CaseScreenHandler).tier
+
+        drawTexture(matrices, x + 42, y + 34, 0, 0, 18, 18)
+
+        drawInvSlots(tier!!, x, y) // Tier should almost certainly be set by the time we are drawing the background
+    }
+
+
+    override fun render(matrices: MatrixStack, mouseX: Int, mouseY: Int, delta: Float) {
+        renderBackground(matrices)
+        super.render(matrices, mouseX, mouseY, delta)
+        drawMouseoverTooltip(matrices, mouseX, mouseY)
+    }
+
+    override fun init() {
+        super.init()
+        val x = (width - backgroundWidth) / 2
+        val y = (height - backgroundHeight) / 2
+        // Center the title
+        titleX = 7
+        val powerButton = TexturedButtonWidget(
+            x + (backgroundWidth / 2) - 18,
+            y + 34,
+            18,
+            18,
+            0,
+            0,
+            0,
+            BUTTON_TEXTURE,
+            36,
+            36
+        ) { button ->
+            TODO(
+                "Computer start/stop here"
+            )
+        }
+        addButton(powerButton)
+    }
+
+    private fun drawInvSlots(tier: Int, x: Int, y: Int) {
+        var invSlotMatrix = MatrixStack()
+
+        client!!.textureManager.bindTexture(SLOT_TEXTURE)
+
+        val xOffset = 93
+        val yOffset = 12
+
+        //drawTexture(invSlotMatrix, x + xOffset, y + yOffset, 0, 0, 18, 18)
+
+        drawTexture(invSlotMatrix, x + xOffset + 3, y + yOffset + 3, 0, 0, 18, 18)
+        drawTexture(invSlotMatrix, x + xOffset + 3, y + yOffset + 21, 0, 0, 18, 18)
+
+        drawTexture(invSlotMatrix, x + xOffset + 3 + 18 + 5, y + yOffset + 3, 0, 0, 18, 18)
+        drawTexture(invSlotMatrix, x + xOffset + 3 + 18 + 5, y + yOffset + 21, 0, 0, 18, 18)
+        drawTexture(invSlotMatrix, x + xOffset + 3 + 18 + 5, y + yOffset + 39, 0, 0, 18, 18)
+
+        drawTexture(invSlotMatrix, x + xOffset + 3 + 36 + 10, y + yOffset + 3, 0, 0, 18, 18)
+    }
+
+    companion object {
+        private val TEXTURE = Identifier(OpenComputers.modId, "textures/gui/background.png")
+        private val COMP_TEXTURE = Identifier(OpenComputers.modId, "textures/gui/computer.png")
+        private val BUTTON_TEXTURE = Identifier(OpenComputers.modId, "textures/gui/button_power.png")
+        private val SLOT_TEXTURE = Identifier(OpenComputers.modId, "textures/gui/slot.png")
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreenHandler.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreenHandler.kt
new file mode 100644
index 0000000000..064385bd9a
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/CaseScreenHandler.kt
@@ -0,0 +1,60 @@
+package li.cli.oc.client.gui.blocks
+
+import li.cli.oc.Components
+import li.cli.oc.client.gui.blocks.slots.*
+import net.minecraft.entity.player.PlayerEntity
+import net.minecraft.entity.player.PlayerInventory
+import net.minecraft.inventory.SimpleInventory
+import net.minecraft.network.PacketByteBuf
+import net.minecraft.screen.ScreenHandler
+import net.minecraft.screen.slot.Slot
+
+class CaseScreenHandler : ScreenHandler {
+    private val inventory = SimpleInventory(10)
+    var tier: Int? = null
+
+    constructor(syncId: Int, playerInventory: PlayerInventory, buf: PacketByteBuf) : this(syncId, playerInventory, buf.readInt()) {
+    }
+
+    constructor(syncId: Int, playerInventory: PlayerInventory, _tier: Int?) : super(Components.CASE_SCREEN_HANDLER, syncId) {
+        if (_tier != null) {
+            this.tier = _tier
+        }
+        addSlot(Slot(inventory, 0, 43, 35)) // EEPROM Slot
+        if (this.tier == 1) {
+            // Two Expansion Slot Cards to the left of the component grid
+            addSlot(Slot(inventory, 1, 97, 16))
+            addSlot(Slot(inventory, 2, 97, 34))
+
+            // One CPU Slot in the center top of the component grid
+            addSlot(Slot(inventory, 3, 120, 16))
+
+            // Two RAM Slots in the direct middle and bottom middle of the component grid
+            addSlot(Slot(inventory, 4, 120, 34))
+            addSlot(Slot(inventory, 5, 120, 52))
+
+            // One HDD Slot in the top right of the component grid
+            addSlot(Slot(inventory, 6, 143, 16))
+        }
+        if (this.tier == 2) {
+            // Two Expansion Slot Cards to the left of the component grid
+            addSlot(Slot(inventory, 1, 97, 16))
+            addSlot(Slot(inventory, 2, 97, 34))
+
+            // One CPU Slot in the center top of the component grid
+            addSlot(Slot(inventory, 3, 120, 16))
+
+            // Two RAM Slots in the direct middle and bottom middle of the component grid
+            addSlot(Slot(inventory, 4, 120, 34))
+            addSlot(Slot(inventory, 5, 120, 52))
+
+            // Two HDD Slots in the top right and middle right of the component grid
+            addSlot(Slot(inventory, 6, 143, 16))
+            addSlot(Slot(inventory, 7, 143, 34))
+        }
+    }
+
+    override fun canUse(player: PlayerEntity?): Boolean {
+        return inventory.canPlayerUse(player)
+    }
+}
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/CPUSlot.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/CPUSlot.kt
new file mode 100644
index 0000000000..8fa131b8f9
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/CPUSlot.kt
@@ -0,0 +1,18 @@
+package li.cli.oc.client.gui.blocks.slots
+
+import li.cli.oc.items.CPU
+import net.minecraft.inventory.Inventory
+import net.minecraft.item.ItemStack
+import net.minecraft.screen.slot.Slot
+
+class CPUSlot(inventory: Inventory, index: Int, x: Int, y: Int, level: Int) : Slot(inventory, index, x, y) {
+    private val tier: Int = 0
+
+/*    override fun canInsert(stack: ItemStack?): Boolean {
+        if (stack != null) {
+            return stack.item is CPU && CPU.tier <= tier
+        }
+
+        return false
+    }*/
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/EEPROMSlot.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/EEPROMSlot.kt
new file mode 100644
index 0000000000..5fbde4a600
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/EEPROMSlot.kt
@@ -0,0 +1,16 @@
+package li.cli.oc.client.gui.blocks.slots
+
+import net.minecraft.inventory.Inventory
+import net.minecraft.item.ItemStack
+import net.minecraft.screen.slot.Slot
+
+class EEPROMSlot(inventory: Inventory, index: Int, x: Int, y: Int) : Slot(inventory, index, x, y) {
+
+/*    override fun canInsert(stack: ItemStack?): Boolean {
+        if (stack != null) {
+            return stack.item is EEPROM // TODO: Rename once BIOS Card item class is created
+        }
+
+        return false
+    }*/
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/ExpSlot.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/ExpSlot.kt
new file mode 100644
index 0000000000..e68d480bf8
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/ExpSlot.kt
@@ -0,0 +1,17 @@
+package li.cli.oc.client.gui.blocks.slots
+
+import net.minecraft.inventory.Inventory
+import net.minecraft.item.ItemStack
+import net.minecraft.screen.slot.Slot
+
+class ExpSlot(inventory: Inventory, index: Int, x: Int, y: Int, level: Int) : Slot(inventory, index, x, y) {
+    private val level: Int = 0
+
+/*    override fun canInsert(stack: ItemStack?): Boolean {
+        if (stack != null) {
+            return stack.item is ExpansionCard && ExpansionCard.level <= level// TODO: Rename once Expansion Card item class is created
+        }
+
+        return false
+    }*/
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/HDSlot.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/HDSlot.kt
new file mode 100644
index 0000000000..b210da3bce
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/HDSlot.kt
@@ -0,0 +1,17 @@
+package li.cli.oc.client.gui.blocks.slots
+
+import net.minecraft.inventory.Inventory
+import net.minecraft.item.ItemStack
+import net.minecraft.screen.slot.Slot
+
+class HDSlot(inventory: Inventory, index: Int, x: Int, y: Int, level: Int) : Slot(inventory, index, x, y) {
+    private val level: Int = 0
+
+/*    override fun canInsert(stack: ItemStack?): Boolean {
+        if (stack != null) {
+            return stack.item is HardDrive && HardDrive.level <= level// TODO: Rename once Expansion Card item class is created
+        }
+
+        return false
+    }*/
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/RAMSlot.kt b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/RAMSlot.kt
new file mode 100644
index 0000000000..f3de09ac61
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/client/gui/blocks/slots/RAMSlot.kt
@@ -0,0 +1,17 @@
+package li.cli.oc.client.gui.blocks.slots
+
+import net.minecraft.inventory.Inventory
+import net.minecraft.item.ItemStack
+import net.minecraft.screen.slot.Slot
+
+class RAMSlot(inventory: Inventory, index: Int, x: Int, y: Int, level: Int) : Slot(inventory, index, x, y) {
+    private val level: Int = 0
+
+/*    override fun canInsert(stack: ItemStack?): Boolean {
+        if (stack != null) {
+            return stack.item is RAMCard && RAMCard.level <= level// TODO: Rename once RAM Card item class is created
+        }
+
+        return false
+    }*/
+}
\ No newline at end of file
diff --git a/src/main/kotlin/li/cli/oc/components/BlockEntitiesComponent.kt b/src/main/kotlin/li/cli/oc/components/BlockEntitiesComponent.kt
index c676de4e6d..7dba86e541 100644
--- a/src/main/kotlin/li/cli/oc/components/BlockEntitiesComponent.kt
+++ b/src/main/kotlin/li/cli/oc/components/BlockEntitiesComponent.kt
@@ -14,7 +14,7 @@ enum class BlockEntitiesComponent(val id: String, val entityType: BlockEntityTyp
     Cable               ("cable",               makeType({ Cable() }, Blocks.Cable)),
     Capacitor           ("capacitor",           makeType({ Capacitor() }, Blocks.Capacitor)),
     CarpatedCapacitor   ("carpetedcapacitor",   makeType({ CarpetedCapacitor() }, Blocks.CarpetedCapacitor)),
-    Case                ("case",                makeType({ CaseEntity()}, Case(4))),
+    Case                ("case",                makeType({ CaseEntity(4)}, Case(4))),
     Charger             ("charger",             makeType({ Charger()}, Blocks.Charger)),
     Disassembler        ("disassembler",        makeType({ Disassembler() }, Blocks.Disassembler)),
     DiskDrive           ("diskdrive",           makeType({ DiskDrive() }, Blocks.DiskDrive)),
diff --git a/src/main/kotlin/li/cli/oc/items/CPU.kt b/src/main/kotlin/li/cli/oc/items/CPU.kt
new file mode 100644
index 0000000000..04be5971bb
--- /dev/null
+++ b/src/main/kotlin/li/cli/oc/items/CPU.kt
@@ -0,0 +1,9 @@
+package li.cli.oc.items
+
+import li.cli.oc.OpenComputers
+import net.minecraft.item.Item
+
+class CPU(tier: Int) : Item(Settings().group(OpenComputers.ITEM_GROUP)) {
+
+    
+}
\ No newline at end of file
diff --git a/src/main/resources/fabric.mod.json b/src/main/resources/fabric.mod.json
index bbea7345e7..2957380cc1 100644
--- a/src/main/resources/fabric.mod.json
+++ b/src/main/resources/fabric.mod.json
@@ -36,7 +36,7 @@
     "fabric": "*",
     "minecraft": "1.16.x"
   },
-  "requires": {
+  "depends": {
     "fabric-language-kotlin": ">=1.4.0"
   },
   "suggests": {