Enemy Path System
Tower defense enemies follow predefined paths rather than using PathfindingService. Create a path using a series of waypoint Parts placed in order. Store waypoints in a Folder sorted by name (Waypoint1, Waypoint2, etc.). Enemies spawn at the first waypoint and move toward each subsequent one using Humanoid:MoveTo() or CFrame interpolation. CFrame-based movement is smoother and more performant than Humanoid movement for large enemy counts. Store the path data in a ModuleScript that both server and client reference. For maps with branching paths, define multiple routes and assign enemies to routes randomly or by type.
Wave System Design
Waves define which enemies spawn, how many, and at what intervals. Store wave data in a ModuleScript as a table of tables — each wave lists enemy types, quantities, spawn delays, and optional modifiers (speed boost, extra health). Start simple with 3-5 enemy types and 20-30 waves. Design difficulty curves that introduce new enemy types gradually. Every 5-10 waves, introduce a boss enemy with high health and special abilities. Between waves, give players 15-30 seconds to place or upgrade towers. Track wave state on the server and replicate the current wave number, enemy count remaining, and countdown timer to all clients.
- Normal enemies — standard health and speed, the baseline
- Fast enemies — low health but high speed, punish gaps in coverage
- Tank enemies — massive health, slow, requires focused firepower
- Flying enemies — skip ground path, only hit by specific tower types
- Boss enemies — appear every 5-10 waves, unique abilities, high rewards
Tower Placement and Grid System
Players need a clear system for placing towers. The most common approach uses a grid-based placement system — divide the map into valid placement zones, snap towers to grid positions, and prevent overlapping placements. When a player selects a tower to place, show a transparent preview model that follows their mouse, with a green tint for valid positions and red for invalid ones. Use raycasting from the mouse position to detect the placement surface. Validate placement on the server before spawning the actual tower — the client preview is just visual feedback. Store placed towers in a server-side table indexed by grid position for fast lookup.
Tower Targeting AI
Each tower needs logic to select and attack enemies within range. Common targeting modes include First (targets the enemy furthest along the path), Strongest (highest health), Weakest (lowest health), and Closest (nearest to the tower). Run targeting logic on the server using a heartbeat loop. For each tower, query all enemies within range using magnitude checks, sort by the selected priority, and fire at the target. Use visual effects to show the attack — projectile parts, beam effects, or instant-hit particles. Apply damage on the server when the attack connects. Towers should smoothly rotate to face their target using CFrame.lookAt for a polished feel.
Upgrade Trees and Economy
Towers should have 3-5 upgrade levels that increase damage, range, attack speed, or add special effects. Each upgrade costs in-game currency earned from killing enemies. Display upgrade paths in a clean UI when the player clicks a placed tower. At higher upgrade levels, offer branching paths — for example, a basic cannon can upgrade into either a rapid-fire variant or a slow, high-damage sniper. This adds strategic depth and replayability. Balance upgrade costs so players face meaningful choices about whether to place new towers or upgrade existing ones.
Co-op Multiplayer
The best Roblox tower defense games support cooperative multiplayer. Multiple players share a map, pool resources, and coordinate tower placement. Run all game logic on the server — wave spawning, enemy movement, damage calculations, and currency distribution. Broadcast state changes to all clients for rendering. Shared currency can be split evenly among players or earned individually. Let players see each other's tower placement previews to coordinate strategy. Add a ready-up system between waves so all players can prepare before the next wave starts.