Guide 13 — A Spark of Corruption

Kathryn Groover

What you're building

An action-adventure platformer across four worlds — Fiery Kingdom, Forest, Ruins, Starry Wastelands — with a party of four: an attacking Fire Aprice, a Servant who moves objects, an Archer who works by stealth and distraction, and an elemental Sorcerer. Shadow creatures oppose you.

Yours is the largest 2D build in the class: character swapping and the full combat stack and four worlds. Your art is also the most developed of anyone's — characters, enemies, and a colour palette per world already designed.

A word before you start: this is a lot. Build one world with two party members completely before adding the rest. A finished quarter of your game beats an unfinished whole one, and everything you learn on world one makes worlds two to four faster.

Time: four-plus hours for the foundation. The rest is content.

1. Before you start

• Finish Guide 0.
• Read Guide B §B1 and §B4.
• Read Guide 12 §3 — your swapping works the same way as Joshua's, with one key difference (section 3).
• One new input action: Dash.

2. Scripts you'll use

Core — Guide B
PlayerController2D · PlayerAnimatorBridge · Health · DamageOnContact · Checkpoint · RespawnManager · CameraTargetAssigner · SceneLoader · GameManager · AudioManager · HUDController · MovingPlatform · ParallaxBackground

Combat (Tier 2)
Team · Hurtbox · Hitbox · Knockback · MeleeAttack · Projectile · ProjectileShooter · EnemyPatrol · EnemyChase · BossController · BossArenaTrigger

Movement (Tier 3)
Dash · DoubleJump · WallSlideJump · Ladder + LadderClimber · GrapplingHook · CharacterDefinition · CharacterSwapper

Level (Tier 4)
Breakable · Door · PuzzleSwitch · SwitchGroup · KillZone · LevelExit · ChoiceFlagManager

Collectibles
ItemType · Collectible · CollectionTracker

3. Shared health or separate?

Joshua's game (Guide 12) gives each character their own health. You have a choice, and it changes the feel:

I'd start with ✗. Your game already has four abilities, four worlds and a combat system — shared health removes one layer of bookkeeping and one whole category of bugs. You can flip the tickbox later; it's one setting.

If you tick ✓, follow Guide 12 §3's death wiring instead of the standard one. If you leave it ✗, wire death normally (Health.OnDied → RespawnManager.OnPlayerDied).

This guide assumes shared health.

4. Build the one player object

Same structure as Guide 12: one object with every ability component, and a CharacterDefinition per party member.

1. Empty GameObject Player, Tag → Player, Sprite Renderer.
2. Rigidbody2D (Gravity Scale 3, Freeze Rotation Z, Continuous), Capsule Collider 2D.
3. Player Input — Behavior: Send Messages.
4. PlayerController2D + GroundCheck child + Ground Layer Ground.
5. Health — Max Health 6, Invulnerability 1.
6. Animator + PlayerAnimatorBridge + Knockback.
7. Every ability component:
   • Dash
   • DoubleJump
   • WallSlideJump (+ a WallCheck child on the right side)
   • LadderClimber
   • GrapplingHook (+ a Rope child with a Line Renderer — Guide 3 §4 has the recipe)
   • MeleeAttack
   • ProjectileShooter (+ a FirePoint child)
8. CharacterSwapper.
9. Children:
   • Hurtbox — trigger collider, Hurtbox (Team Player), layer Hurtbox
   • AttackHitbox — trigger collider in front, Hitbox (Target Enemy, Damage 1, Knockback 8), layer Hitbox, GameObject unticked

Wire the components to their children

• MeleeAttack → Hitbox = AttackHitbox; Windup 0.08 / Active 0.12 / Recovery 0.2
• ProjectileShooter → Fire Point = FirePoint; Team = Player; Mode = Manual (see the warning below)
• WallSlideJump → Wall Check = the child; Wall Layer Ground
• GrapplingHook → Rope = the child; Grapple Layer Ground; Aim Facing

⚠️ MeleeAttack and ProjectileShooter both listen to Attack. With the shooter in PlayerInput mode, your Fire Aprice would swing and shoot. Set the shooter to Manual, then either add a separate Shoot action (ask for the two-line script that calls Fire()), or accept that ranged characters shoot on Attack and melee ones swing — by disabling whichever component that character doesn't use. The second option needs no script, and it's what the character definitions below assume.

5. Create the four party members

Right-click Project → Create → GAME1303 → Character, four times. Enabled Abilities holds component class names as exact text.

Fire Aprice — attack

The Servant — support, moves objects

Your sketch describes the Servant as flying/moving objects — the grappling hook is the closest fit in the kit, and it doubles as a traversal tool. It can pull the Servant to anchors and be your "move things" verb if you place grabbable anchors on objects.

The Archer — support, stealth and distraction

The Sorcerer — attack/support, elemental

The Archer and Sorcerer both shoot — differentiate them with two bullet prefabs and swap which one ProjectileShooter uses. Simplest version: give the Sorcerer a slower, higher-damage, piercing projectile and the Archer a fast, weak, rapid one. That needs one line of a helper script or you can leave both the same for now and differentiate by animation.

Animator warning

All four controllers must use identical parameter names. Build one, duplicate it three times, change only the clips. Mismatched names silently reset animation on every swap.

6. Configure the swapper

On Player, CharacterSwapper:

Add Character1–Character4 input actions bound to 1–4 if you want direct selection. Q/E cycling works out of the box.

7. Build the shadow enemies

Your sketch shows shadow blobs. Three variants:

Shadow crawler — Guide B §B4: EnemyPatrol (Sensors), Health 3, Hurtbox (Team Enemy), BodyHitbox (Damage 1, Repeat Delay 1). Invulnerability 0.

Shadow drifter — Rigidbody2D Gravity Scale 0, FloatingEnemy (Wander, radius 4), EnemyChase (Movement Free, Detect 6, Speed 3).

Shadow archer — a crawler plus ProjectileShooter (Team Enemy, Mode AutoFire, Aim TowardPlayer, Fire Rate 2) and a FirePoint child. Needs an enemy bullet prefab: Rigidbody2D (Gravity 0) + trigger collider + Projectile (Damage 1, Speed 10, Blocking Layers Ground).

Give each world a tinted variant using its palette — same prefab, different Sprite Renderer colour. Four worlds of enemies for almost no extra work.

8. Build world one

Pick one world (I'd suggest Fiery Kingdom, since it's first in your art) and build it completely.

• Ground on Ground with colliders; include vertical walls so the Archer's wall-slide matters
• KillZone underneath
• Checkpoints
• Ladders for the Sorcerer
• Grapple anchors for the Servant — just Ground-layer platforms placed out of jump range
• Breakable walls: sprite + Rigidbody2D + collider + Health (3) + Breakable (Min Damage To Break 2) + a Hurtbox child with Team = Neutral
• PuzzleSwitch + Door pairs
• LevelExit
• Camera per Guide B §B3, with a confiner

Puzzles that need the party

This is where your design earns its four characters:

The two-switch puzzle

1. Two PuzzleSwitch objects, One Shot ✗, Activation Stand.
2. Empty GameObject SwitchGroup + the SwitchGroup component. Drag both switches in, Required 0 (means all), Reset If Broken ✓.
3. Wire SwitchGroup.OnGroupComplete → Door.Open.

With Reset If Broken ticked, the player has to hold both — which needs a pushable object or careful timing. Without it, they can press them in sequence.

9. The HUD

1. Canvas → PortraitImage, NameText, a health bar Slider, an item counter if you have collectibles.
2. Empty child HUD with HUDController; assign the health bar.
3. Wire CharacterSwapper.OnCharacterChanged to update the portrait — this needs a two-line script since the event sends a CharacterDefinition. Ask for it; it's the readout your mechanic depends on.

A stand-in that needs no script: four small portrait Images always visible, with a highlight frame you move. Not automatic, but it shows the whole party at once, which is arguably better.

10. Wire it up

(If you chose separate health in section 3, swap row 1 for Guide 12's two rows.)

11. First playtest

Small room: a ladder, a wall, a grapple anchor, a breakable wall, two shadow crawlers.

1. Q/E cycle all four party members, and the sprite/stats change.
2. Only Aprice can melee. Swap to the Archer and press Attack — she should shoot, not swing.
3. Only the Servant can grapple.
4. Only the Archer can wall-slide.
5. Only the Sorcerer can climb.
6. A projectile breaks the Breakable wall; a melee hit doesn't (Min Damage To Break 2).
7. Shadow enemies patrol, chase and shoot.
8. Switches open doors.
9. The camera follows and stays in bounds.

Steps 2–5 are the mechanic. If everyone can do everything, your Enabled Abilities lists have typos or the Ability Components list was filled manually.

12. Then add

1. Finish world one. Levels, puzzles, a boss.
2. A boss — Guide 7 §9 recipe, Resistance 1, two phases.
3. Animation — four controllers, identical parameters. This is your biggest remaining art job.
4. ParallaxBackground per world, using your palettes. Fiery Kingdom warm, Forest green, Ruins grey, Starry Wastelands blue-violet — this is where your colour work pays off most visibly.
5. Worlds two to four — duplicate the scene, restyle, redesign. Much faster the second time.
6. Collectibles if you want optional content: an ItemType, pickups, a counter.
7. Dialogue between party members using Guide 10 §5's panel — your characters have distinct designs and deserve voices.

13. Design notes for your game specifically

Scope is your real challenge, not any single system. Four worlds × four characters × full combat is more than a semester. The good news is that the systems are done once world one works — everything after is content, and content can be trimmed without breaking anything. Build one complete world and treat the others as stretch goals. A polished Fiery Kingdom with a boss is a better portfolio piece than four rough ones.

Your abilities need to be required, not just available. Right now they're four ways to play. The design gets interesting when a room needs the Servant, and the player has to think "which of my four" rather than "which do I like." One required-ability puzzle per section is enough to make swapping habitual.

Attack/Support is a good frame — use it in your level design. Your sketch labels each character. Design encounters where an attacker alone loses: shadow archers on a ledge the Servant must grapple to, or a group that must be distracted before it can be fought. That's what makes a party rather than four skins.

Min Damage To Break is your quiet puzzle tool. A wall that ignores a sword but yields to a sorcerer's bolt is a locked door that needs no key and no explanation. Cheap, readable, and it teaches the player to think about who they're playing as.

Your four palettes are an asset most people don't have. Enemy tinting, parallax layers, and lighting per world means each one feels distinct with no new art. Push that further than you think you need to — a player should know which world they're in from a single screenshot.

14. Common problems

15. Checklist

• Health decision made (shared recommended) and death wired to match
• One player object with all seven ability components
• Four CharacterDefinition assets with correct Enabled Abilities spelling
• MeleeAttack → AttackHitbox; ProjectileShooter → Manual + FirePoint
• WallSlideJump → WallCheck; GrapplingHook → Rope with a material
• Four Animator Controllers with identical parameters (or none yet)
• Three shadow enemy types, one ranged
• World one only, with one puzzle per party member
• Breakable with Min Damage To Break 2
• A SwitchGroup puzzle
• Playtest steps 2–5 all pass
• Boss and remaining worlds treated as stretch goals