init, working screens from raylib screens example and basic bullets mechanics

main.odin

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+package space_invaders
+
+import "core:c"
+import "core:log"
+import glm "core:math/linalg/glsl"
+
+import rl "vendor:raylib"
+
+// orignal resolution of space invaders
+// 256 x 224 px
+
+GameState :: struct {
+	// window
+	target_fps:         c.int,
+	title:              cstring,
+	screen_width:       c.int,
+	screen_height:      c.int,
+	// frame stats
+	frame_counter:      int,
+	current_frame_time: f64,
+	last_frame_time:    f64,
+	delta_time:         f64,
+	// game vars
+	screen:             GameScreen,
+	previous_screen:    GameScreen,
+	last_frame_screen:  GameScreen,
+	aliens:             #soa[ALIENS]Alien,
+	bullets:            #soa[MAX_BULLETS]Bullet,
+	bullet_index:       int,
+	player_pos:         glm.vec2,
+	player_health:      c.int,
+	player_score:       c.int,
+}
+state: GameState
+
+setup :: proc(state: ^GameState) {
+	using state
+	target_fps = 60
+	screen_width = 800
+	screen_height = 600
+	title = "Space Invaders (raylib+odin-lang edition)"
+
+	current_frame_time = rl.GetTime()
+	previous_screen = .LOGO
+	screen = .GAMEPLAY
+
+	rl.SetTargetFPS(target_fps)
+}
+
+update :: proc(state: ^GameState) {
+	using state
+
+	frame_counter += 1
+
+	last_frame_time = current_frame_time
+	current_frame_time = rl.GetTime()
+	delta_time = current_frame_time - last_frame_time
+
+	update_screen(state)
+}
+
+draw :: proc(state: ^GameState) {
+	rl.BeginDrawing()
+	rl.ClearBackground(rl.RAYWHITE)
+	draw_screen(state)
+	rl.EndDrawing()
+}
+
+main :: proc() {
+	context.logger = log.create_console_logger()
+
+	log.info(state.screen)
+
+	setup(&state)
+
+	rl.InitWindow(state.screen_width, state.screen_height, state.title)
+	defer rl.CloseWindow()
+
+	for !rl.WindowShouldClose() {
+		update(&state)
+		draw(&state)
+	}
+}