Added some templates for events.

core/src/commonMain/kotlin/cn/rdlevel/rdkt/core/events/CustomEvent.kt

@@ -0,0 +1,17 @@
+package cn.rdlevel.rdkt.core.events
+
+import cn.rdlevel.rdkt.core.RDLevel
+
+/**
+ * An event that can be customized by the developers.
+ * Developers are encouraged to use this interface to create their own custom events.
+ */
+public abstract class CustomEvent : AbstractEvent() {
+    /**
+     * Applies this event to the given level.
+     * This method should be overridden by custom events to define how they affect the level.
+     *
+     * @param level The level to apply this event to.
+     */
+    public abstract fun applyToLevel(level: RDLevel)
+}

core/src/commonMain/kotlin/cn/rdlevel/rdkt/core/events/Event.kt

@@ -1,4 +1,57 @@
 package cn.rdlevel.rdkt.core.events
 
-public interface Event {
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/**
+ * A base event interface. Custom levels use events to perform actions.
+ */
+@Serializable
+public sealed interface Event {
+    /**
+     * The bar the event is in.
+     */
+    public var bar: Int
+
+    /**
+     * The beat the event is in.
+     * Note that this is immutable by default. See [BeatSpecificEvent] for the mutable version.
+     */
+    public val beat: Double
+        get() = 1.0
+
+    /**
+     * Whether the event will be executed or not.
+     */
+    public var active: Boolean
+
+    /**
+     * The tag of the event.
+     * Can be used to group events together.
+     */
+    @SerialName("Tag")
+    public var tag: String?
+
+    /**
+     * Whether the event should be run on its position even when a [tag] is set.
+     * By default, tagged events are not run on their position.
+     */
+    public var runTag: Boolean
+}
+
+/**
+ * An abstraction of an [Event] that provides default implementations for some properties.
+ */
+public sealed class AbstractEvent: Event {
+    override var bar: Int = 1
+        set(value) {
+            require(value >= 1) { "Bar must be greater than or equal to 1." }
+            field = value
+        }
+
+    override var active: Boolean = true
+
+    override var tag: String? = null
+
+    override var runTag: Boolean = false
 }

core/src/commonMain/kotlin/cn/rdlevel/rdkt/core/events/EventProperties.kt

@@ -0,0 +1,33 @@
+package cn.rdlevel.rdkt.core.events
+
+/**
+ * An [Event] that can specify a beat manually.
+ */
+public interface BeatSpecificEvent : Event {
+    /**
+     * The beat the event is in.
+     * This property is mutable, allowing the beat to be set directly.
+     */
+    override var beat: Double
+}
+
+/**
+ * An [Event] that is specific to a Y position, aka the row position in the editor.
+ */
+public interface YSpecificEvent : Event {
+    /**
+     * The Y position the event is in.
+     * Setting this to negative values will hide the event from the editor.
+     */
+    public var y: Int
+}
+
+/**
+ * An [Event] that has a duration, meaning it lasts for a certain number of beats.
+ */
+public interface DurationSpecificEvent : Event {
+    /**
+     * The duration of the event in beats.
+     */
+    public var duration: Double
+}

core/src/commonMain/kotlin/cn/rdlevel/rdkt/core/events/EventTabs.kt

@@ -0,0 +1,28 @@
+package cn.rdlevel.rdkt.core.events
+
+/**
+ * An event that belongs to the sounds tab.
+ */
+public sealed class SoundEvent : AbstractEvent(), YSpecificEvent {
+    override var y: Int = 0
+}
+
+/**
+ * An event that belongs to the rows tab.
+ */
+public sealed class RowEvent : AbstractEvent()
+
+/**
+ * An event that belongs to the actions tab.
+ */
+public sealed class ActionEvent : AbstractEvent()
+
+/**
+ * An event that belongs to the rooms tab.
+ */
+public sealed class RoomEvent : AbstractEvent()
+
+/**
+ * An event that belongs to the decorations tab.
+ */
+public sealed class DecorationEvent : AbstractEvent()