Update README.md

README.md

@@ -1,6 +1,92 @@
 # About
 Ento is an Entity Component System written in Go.
 
+# Getting Started
+
+See [examples](./examples) folder.
+
+From [hello.go](./examples/hello/hello.go):
+
+```go
+package main
+
+type Component1 struct{ value int }
+type Component2 struct{ value int }
+type Component3 struct{ value int }
+
+type System struct {
+	// Always use pointer to base component type (!)
+	// Add `ento:"bind"` tag to automatically bind components
+	Component1 *Component1 `ento:"bind"`
+
+	// Components are bound by type, not name
+	Renamed *Component2 `ento:"bind"`
+
+	// Systems can have non-component-bound fields
+	calls int
+}
+
+// Update implements ento.System
+// It will be called only for entities that have both tagged components
+func (s *System) Update(entity *ento.Entity) {
+	// Access automatically bound components from currently passed entity
+	s.Component1.value += s.Renamed.value
+
+	// Get components from entity manually (somewhat slower than automatic binding)
+	// Can be used for "optional" components
+	var c3 *Component3
+	entity.Get(&c3)
+
+	// If entity does not have the component, the pointer value will be set to nil
+	if c3 != nil {
+		s.Component1.value += c3.value
+	}
+
+	s.calls++
+}
+
+func (s *System) reportCalls() {
+	println(s.calls)
+	s.calls = 0
+}
+
+func main() {
+	// Create the world and register components
+	world := ento.NewWorldBuilder().
+		// Use "zero-values" as values are ignored when registering
+		WithSparseComponents(Component1{}, Component2{}, Component3{}).
+		// Pre-allocate space for 256 entities (world can grow beyond that automatically)
+		Build(256)
+
+	// Add systems
+	system := &System{}
+	world.AddSystems(system)
+
+	// Create entities (they are added to the world immediately)
+	world.NewEntity(Component1{1}, Component2{2}, Component3{3})
+
+	// Use Set to add or update their components
+	entity := world.NewEntity()
+	entity.Set(Component1{0}) // Will not be handled by System
+
+	// Update the world
+	world.Update()
+	system.reportCalls() // Prints: 1
+
+	// Update the entity (add Component2)
+	entity.Set(Component2{5})
+
+	world.Update()
+	system.reportCalls() // Prints: 2
+
+	// Update the entity (remove Component2)
+	entity.Rem(Component2{})
+
+	world.Update()
+	system.reportCalls() // Prints: 1
+}
+```
+
 # License
 
 Ento is distributed under MIT license.