diff --git a/game/commands.odin b/game/commands.odin
index e906498..18431fc 100644
--- a/game/commands.odin
+++ b/game/commands.odin
@@ -6,6 +6,7 @@ Command_Kind :: enum {
 	None,
 	Place_Tower,
 	Start_Wave,
+	Upgrade_Tower,
 }
 
 Command :: struct {
@@ -25,6 +26,12 @@ gather_commands :: proc(world: ^World) -> Command {
 		return Command{kind = .Start_Wave}
 	}
 
+	if rl.IsMouseButtonPressed(.RIGHT) {
+		mouse := game_mouse()
+		gx, gy := screen_to_grid(mouse.x, mouse.y)
+		return Command{kind = .Upgrade_Tower, gx = gx, gy = gy}
+	}
+
 	if world.phase == .Build && rl.IsMouseButtonPressed(.LEFT) {
 		mouse := game_mouse()
 		gx, gy := screen_to_grid(mouse.x, mouse.y)
@@ -41,6 +48,8 @@ execute_command :: proc(world: ^World, cmd: Command) {
 		try_place_tower(world, cmd.gx, cmd.gy, world.selected_tower)
 	case .Start_Wave:
 		start_wave(world)
+	case .Upgrade_Tower:
+		try_upgrade_tower(world, cmd.gx, cmd.gy)
 	}
 }
 
diff --git a/game/tower.odin b/game/tower.odin
index 5b86c2f..6576617 100644
--- a/game/tower.odin
+++ b/game/tower.odin
@@ -1,13 +1,15 @@
 package game
 
+import "core:fmt"
 import rl "vendor:raylib"
 
 Tower :: struct {
-	position:  Vec2,
-	kind:      Tower_Kind,
-	cooldown:  f32,
-	anchor_gx: int,
-	anchor_gy: int,
+	upgrade_level: int,
+	position:      Vec2,
+	kind:          Tower_Kind,
+	cooldown:      f32,
+	anchor_gx:     int,
+	anchor_gy:     int,
 }
 
 Tower_Kind :: enum {
@@ -17,13 +19,17 @@ Tower_Kind :: enum {
 }
 
 Tower_Archetype :: struct {
-	kind:        Tower_Kind,
-	range:       f32,
-	damage:      int,
-	fire_rate:   f32,
-	cost:        int,
-	footprint_w: int, // 1 column wide
-	footprint_h: int, // two rows tall
+	kind:             Tower_Kind,
+	range:            f32,
+	damage:           int,
+	fire_rate:        f32,
+	cost:             int,
+	footprint_w:      int, // 1 column wide
+	footprint_h:      int, // two rows tall
+	max_upgrade:      int,
+	upgrade_cost:     int,
+	damage_per_level: int,
+	range_per_level:  f32,
 }
 
 TOWER_ARCHETYPES: [Tower_Kind]Tower_Archetype = {
@@ -35,6 +41,10 @@ TOWER_ARCHETYPES: [Tower_Kind]Tower_Archetype = {
 		cost = TOWER_COST,
 		footprint_w = 1,
 		footprint_h = 2,
+		max_upgrade = 1,
+		upgrade_cost = 40,
+		damage_per_level = 3,
+		range_per_level = 8,
 	},
 	.Cannon = {
 		kind = .Cannon,
@@ -44,6 +54,9 @@ TOWER_ARCHETYPES: [Tower_Kind]Tower_Archetype = {
 		cost = 80,
 		footprint_w = 2,
 		footprint_h = 2,
+		upgrade_cost = 40,
+		damage_per_level = 3,
+		range_per_level = 8,
 	},
 	.Ice = {
 		kind = .Ice,
@@ -53,9 +66,19 @@ TOWER_ARCHETYPES: [Tower_Kind]Tower_Archetype = {
 		cost = 65,
 		footprint_w = 1,
 		footprint_h = 1,
+		upgrade_cost = 40,
+		damage_per_level = 3,
+		range_per_level = 8,
 	},
 }
 
+tower_stats_at_level :: proc(tower: Tower) -> (damage: int, range: f32) {
+	arch := get_archetype(tower.kind)
+	damage = arch.damage + tower.upgrade_level * arch.damage_per_level
+	range = arch.range + f32(tower.upgrade_level) * arch.range_per_level
+	return
+}
+
 can_place_tower :: proc(world: ^World, gx, gy: int, kind: Tower_Kind) -> bool {
 	if world.phase != .Build do return false
 	arch := get_archetype(kind)
@@ -124,6 +147,22 @@ get_archetype :: proc(kind: Tower_Kind) -> Tower_Archetype {
 	return TOWER_ARCHETYPES[kind]
 }
 
+try_upgrade_tower :: proc(world: ^World, gx, gy: int) -> bool {
+	if world.phase != .Build do return false
+	t := tower_at_grid(world, gx, gy)
+	if t == nil do return false
+
+	arch := get_archetype(t.kind)
+	if t.upgrade_level >= arch.max_upgrade do return false
+
+	cost := arch.upgrade_cost + t.upgrade_level * 25
+	if world.gold < cost do return false
+
+	world.gold -= cost
+	t.upgrade_level += 1
+	return true
+}
+
 try_place_tower :: proc(world: ^World, gx, gy: int, kind: Tower_Kind) -> bool {
 	if !can_place_tower(world, gx, gy, kind) do return false
 
@@ -142,8 +181,21 @@ try_place_tower :: proc(world: ^World, gx, gy: int, kind: Tower_Kind) -> bool {
 	return true
 }
 
+tower_at_grid :: proc(world: ^World, gx, gy: int) -> ^Tower {
+	for i in 0 ..< len(world.towers) {
+		t := &world.towers[i]
+		arch := get_archetype(t.kind)
+		if gx >= t.anchor_gx &&
+		   gx < t.anchor_gx + arch.footprint_w &&
+		   gy >= t.anchor_gy &&
+		   gy < t.anchor_gy + arch.footprint_h {
+			return t
+		}
+	}
+	return nil
+}
+
 find_target_slot :: proc(tower: Tower, world: ^World) -> int {
-	arch := get_archetype(tower.kind)
 	best_slot: int = -1
 	best_dist: f32 = 999999
 
@@ -153,7 +205,8 @@ find_target_slot :: proc(tower: Tower, world: ^World) -> int {
 		if e.path_index >= len(world.path) do continue
 
 		d := distance(tower.position, e.position)
-		if d <= arch.range && d < best_dist {
+		_, range := tower_stats_at_level(tower)
+		if d <= range && d < best_dist {
 			best_slot = i
 			best_dist = d
 		}
@@ -173,16 +226,17 @@ update_towers :: proc(world: ^World, dt: f32) {
 
 		arch := get_archetype(t.kind)
 
+		damage, _ := tower_stats_at_level(t^)
 		switch t.kind {
 		case .Archer:
-			spawn_projectile(world, t.position, slot, arch.damage)
+			spawn_projectile(world, t.position, slot, damage)
 		case .Cannon:
 			if target := enemy_at_slot(world, slot); target != nil {
-				apply_tower_hit(world, target, arch.damage)
+				apply_tower_hit(world, target, damage)
 			}
 		case .Ice:
 			if target := enemy_at_slot(world, slot); target != nil {
-				apply_ice_hit(world, target, arch.damage)
+				apply_ice_hit(world, target, damage)
 			}
 		}
 		t.cooldown = arch.fire_rate
@@ -224,6 +278,10 @@ render_towers :: proc(world: ^World) {
 			i32(pixel_height),
 			color,
 		)
+		if t.upgrade_level > 0 {
+			label := fmt.ctprintf("Lv%d", t.upgrade_level + 1) // or just t.upgrade_level
+			rl.DrawText(label, i32(t.position.x), i32(t.position.y), 14, rl.WHITE)
+		}
 	}
 }