diff --git a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Setting.kt b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Setting.kt
new file mode 100644
index 000000000..c6d68e2cf
--- /dev/null
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Setting.kt
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:Suppress("INVISIBLE_REFERENCE", "INVISIBLE_MEMBER", "EXPOSED_SUPER_CLASS")
+
+package net.mamoe.mirai.console.setting
+
+import net.mamoe.mirai.console.setting.internal.cast
+import net.mamoe.mirai.console.setting.internal.valueFromKTypeImpl
+import kotlin.internal.LowPriorityInOverloadResolution
+import kotlin.reflect.KProperty
+import kotlin.reflect.typeOf
+
+
+// Shows public APIs such as deciding when to auto-save.
+abstract class Setting : SettingImpl()
+
+/**
+ * Internal implementation for [Setting] including:
+ * - Reflection on Kotlin properties and Java fields
+ * - Auto-saving
+ */
+// TODO move to internal package.
+internal abstract class SettingImpl {
+    private class Node<T>(
+        val property: KProperty<T>,
+        val value: Value<T>,
+        val serializer: ValueSerializer<T>
+    )
+
+    private val valueNodes: List<Node<*>> = kotlin.run {
+        TODO("reflection")
+    }
+}
+
+
+//// region Setting.value primitives CODEGEN START ////
+
+// TODO: 2020/6/19 CODEGEN
+
+fun Setting.value(value: Int): IntValue = TODO("codegen")
+
+//// endregion Setting.value primitives CODEGEN END ////
+
+
+/**
+ * Creates a [Value] with [default].
+ *
+ * @param T reified param type T.
+ * Supports only primitives, Kotlin built-in collections,
+ * and classes that are serializable with Kotlinx.serialization
+ * (typically annotated with [kotlinx.serialization.Serializable])
+ */
+@LowPriorityInOverloadResolution
+@OptIn(ExperimentalStdlibApi::class) // stable in 1.4
+inline fun <reified T> Setting.value(default: T): Value<T> = valueFromKTypeImpl(typeOf<T>()).cast()
\ No newline at end of file
diff --git a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Value.kt b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Value.kt
new file mode 100644
index 000000000..cdedff4b1
--- /dev/null
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/Value.kt
@@ -0,0 +1,142 @@
+@file:Suppress("INVISIBLE_REFERENCE", "INVISIBLE_MEMBER")
+
+package net.mamoe.mirai.console.setting
+
+import kotlinx.serialization.KSerializer
+import net.mamoe.mirai.console.setting.internal.cast
+import net.mamoe.mirai.console.setting.internal.valueFromKTypeImpl
+import net.mamoe.mirai.utils.MiraiExperimentalAPI
+import kotlin.internal.LowPriorityInOverloadResolution
+import kotlin.reflect.typeOf
+
+/**
+ * Represents a observable, immutable value wrapping.
+ *
+ * The value can be modified by delegation just like Kotlin's `var`, however it can also be done by the user, e.g. changing using the UI frontend.
+ *
+ * Some frequently used types are specially treated with performance enhancement by codegen.
+ *
+ * @see PrimitiveValue
+ * @see CompositeValue
+ */
+interface Value<T> {
+    var value: T
+}
+
+/**
+ * The serializer for a specific kind of [Value].
+ */
+typealias ValueSerializer<T> = KSerializer<Value<T>>
+
+/**
+ * Represents a observable *primitive* value wrapping.
+ *
+ * 8 types that are considered *primitive*:
+ * - Integers: [Byte], [Short], [Int], [Long]
+ * - Floating: [Float], [Double]
+ * - [Boolean]
+ * - [Char], [String]
+ *
+ * Note: The values are actually *boxed* because of the generic type T.
+ * *Primitive* indicates only it is one of the 8 types mentioned above.
+ */
+interface PrimitiveValue<T> : Value<T>
+
+interface MutablePrimitiveValue<T> : Value<T>
+
+
+//// region PrimitiveValue CODEGEN START ////
+
+// TODO: 2020/6/19 CODEGEN
+
+/**
+ * Represents a non-null [Int] value.
+ */
+interface IntValue : PrimitiveValue<Int>
+
+//// endregion PrimitiveValue CODEGEN END ////
+
+
+@MiraiExperimentalAPI
+interface CompositeValue<T> : Value<T>
+
+/**
+ * Superclass of [CompositeListValue], [PrimitiveListValue].
+ */
+interface ListValue<T> : CompositeValue<List<T>>
+
+/**
+ * Elements can by anything, wrapped as [Value].
+ * @param T is not primitive types.
+ */
+interface CompositeListValue<T> : ListValue<Value<T>>
+
+/**
+ * Elements can only be primitives, not wrapped.
+ * @param T is not primitive types.
+ */
+interface PrimitiveListValue<T> : ListValue<T>
+
+
+//// region PrimitiveListValue CODEGEN START ////
+
+interface PrimitiveIntListValue<T> : PrimitiveListValue<T>
+interface PrimitiveLongListValue<T> : PrimitiveListValue<T>
+// TODO + codegen
+
+//// endregion PrimitiveListValue CODEGEN END ////
+
+
+/**
+ * Superclass of [CompositeSetValue], [PrimitiveSetValue].
+ */
+interface SetValue<T> : CompositeValue<Set<T>>
+
+/**
+ * Elements can by anything, wrapped as [Value].
+ * @param T is not primitive types.
+ */
+interface CompositeSetValue<T> : SetValue<Value<T>>
+
+/**
+ * Elements can only be primitives, not wrapped.
+ * @param T is not primitive types.
+ */
+interface PrimitiveSetValue<T> : SetValue<T>
+
+
+//// region PrimitiveSetValue CODEGEN START ////
+
+interface PrimitiveIntSetValue<T> : PrimitiveSetValue<T>
+interface PrimitiveLongSetValue<T> : PrimitiveSetValue<T>
+// TODO + codegen
+
+//// endregion PrimitiveSetValue CODEGEN END ////
+
+
+/**
+ * Superclass of [CompositeMapValue], [PrimitiveMapValue].
+ */
+interface MapValue<K, V> : CompositeValue<Map<K, V>>
+
+interface CompositeMapValue<K, V> : MapValue<Value<K>, Value<V>>
+
+interface PrimitiveMapValue<K, V> : MapValue<K, V>
+
+
+//// region PrimitiveMapValue CODEGEN START ////
+
+interface PrimitiveIntIntMapValue : PrimitiveMapValue<Int, Int>
+interface PrimitiveIntLongMapValue : PrimitiveMapValue<Int, Long>
+// TODO + codegen
+
+//// endregion PrimitiveSetValue CODEGEN END ////
+
+
+
+
+
+
+
+
+
diff --git a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueCreatorsImpl.kt b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueCreatorsImpl.kt
new file mode 100644
index 000000000..e6d80c495
--- /dev/null
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueCreatorsImpl.kt
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:Suppress("NOTHING_TO_INLINE")
+
+package net.mamoe.mirai.console.setting.internal
+
+import net.mamoe.mirai.console.setting.Setting
+import net.mamoe.mirai.console.setting.Value
+import kotlin.reflect.KClass
+import kotlin.reflect.KType
+import kotlin.reflect.full.isSubclassOf
+
+
+@PublishedApi
+internal fun Setting.valueFromKTypeImpl(type: KType): Value<*> {
+    require(type.classifier is KClass<*>)
+
+    if (type.classifier.isPrimitiveOrBuiltInSerializableValue()) {
+        TODO("是基础类型, 可以直接创建 ValueImpl. ")
+    }
+
+    // 复合类型
+
+    when {
+        type.classifier.isSubclassOf(Map::class) -> {
+
+            TODO()
+        }
+        type.classifier.isSubclassOf(List::class) -> {
+
+            TODO()
+        }
+        type.classifier.isSubclassOf(Set::class) -> {
+            TODO()
+        }
+        else -> error("Custom composite value is not supported yet (${type.classifier.qualifiedName})")
+    }
+}
+
+internal fun KClass<*>.isPrimitiveOrBuiltInSerializableValue(): Boolean {
+    when (this) {
+        Byte::class, Short::class, Int::class, Long::class,
+        Boolean::class,
+        Char::class, String::class,
+        Pair::class, Triple::class
+        -> return true
+    }
+
+    return false
+}
+
+@PublishedApi
+@Suppress("UNCHECKED_CAST")
+internal inline fun <R, T> T.cast(): R = this as R
\ No newline at end of file
diff --git a/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueDeclarationsImpl.kt b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueDeclarationsImpl.kt
new file mode 100644
index 000000000..ce7a68627
--- /dev/null
+++ b/backend/mirai-console/src/main/kotlin/net/mamoe/mirai/console/setting/internal/ValueDeclarationsImpl.kt
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+@file:Suppress("unused")
+
+package net.mamoe.mirai.console.setting.internal
+
+import net.mamoe.mirai.console.setting.CompositeListValue
+import net.mamoe.mirai.console.setting.IntValue
+import net.mamoe.mirai.console.setting.Value
+
+internal abstract class IntValueImpl : IntValue {
+    constructor()
+    constructor(default: Int) {
+        _value = default
+    }
+
+    private var _value: Int? = null
+
+    override var value: Int
+        get() = _value ?: throw IllegalStateException("IntValue should be initialized before get.")
+        set(v) {
+            if (v != this._value) {
+                this._value = v
+                onChanged()
+            }
+        }
+
+    protected abstract fun onChanged()
+}
+
+internal abstract class CompositeListValueImpl<T>(
+    val tToValue: (T) -> Value<T>
+) : CompositeListValue<T> {
+    private var _value: List<Value<T>> = mutableListOf()
+    override var value: List<Value<T>>
+        get() = _value
+        set(v) {
+            _value = v
+        }
+}
\ No newline at end of file