Merge Downhill

Why this works

The game combines three mechanics that are individually proven top-100 performers.

Audience

• Primary: 9–15, mobile-first — Roblox mobile is ~70% of DAU.
• Secondary: 16–24, the "satisfying content" / cozy destruction audience.
• Region: Global English, fully localized. Low-text game = cheap localization.

Non-goals (v1)

• No combat or PvP
• No building or placement mechanics
• No open world — the ramp is the world
• No complex crafting trees

Physical structure

Slope varies along the length — flat sections, steep drops, curves, and jumps. Player is locked to a platform at the top; camera follows the object or stays put (player's choice).

The drop — 3 parameters

1. Lane — left, center, or right, each with different obstacle density
2. Launch force — from an upgrade, adds initial velocity
3. Angle — unlocked in World 3, adds a light skill layer

The roll

A run ends when the object stops (velocity below threshold for 1.5s), reaches the bottom collection zone (best case, bonus multiplier), or hits a 20-second hard timeout.

The payoff

Numbers count up with sound. This is load-bearing game feel — do not ship it flat.

Variants

Every tier can roll a variant on purchase — the collection layer and main long-tail retention driver.

Merge rule: same-variant preserves it; mixed yields the lower. Creates real decision-making.

Announcement: Void/Rainbow drops trigger server-wide chat with the player's name. Free social pressure.

Level design rules

1. Density increases toward the bottom. Early ramp is sparse; bottom third is the climax.
2. Every 200 studs has one moment — a jump, a big destructible, or a hazard.
3. Sightlines matter. Player must see 400+ studs ahead from the top.
4. Readability over realism. Destructible = bright & saturated; static = desaturated.
5. Bottom is a spectacle zone. Wide open, max density, confetti + coin explosion on arrival.

Combo

Every obstacle destroyed within 1.2s of the previous one increments the combo.

comboMultiplier = 1 + (comboCount × 0.08)   -- capped at ×10

Screen edges warm up at ×3, percussion layer at ×6, full intensity at ×9.

Run payout formula

runPayout = objectBaseValue × variantMult × worldMult
           × (1 + obstacleValue) × comboMult × distanceBonus
           × upgradeMult × petMult × rebirthMult × gamepassMult

All multipliers are multiplicative — intentional. Makes stacking feel powerful, drives gamepass attach.

Currencies

Anti-inflation guards

• All currency operations are server-authoritative
• Payout capped per run at 200× object base value
• Rate limit: 4 drops/second/player, server-enforced

Rules

• Two same-tier objects → one of the next tier
• Same variant preserves; mixed → lower variant
• Auto-Merge (gamepass) fuses automatically when matches exist
• Merge Luck: 3% base double-merge chance. Big VFX + sound — this is the jackpot moment.

Systems

• Slots: 3 base, up to 8 via gamepass and upgrades
• Fusing: 5 identical → Golden (×2.5); 5 Goldens → Rainbow (×6). The long-tail chase.
• Crates: Gems or Robux, world-specific pools
• Trading: gated behind 24hr account age + level 10 (anti-scam/bot)

Unlocks at World 5, Tier 20.

coresEarned = floor(3 × rebirthNumber^0.85) + 5
permanentMultiplier = 1 + (0.35 × totalRebirths)

Rebirth 1 → ×1.35, rebirth 10 → ×4.5, rebirth 50 → ×18.5. Curve flattens deliberately — late rebirths are about Cores and cosmetics.

Total value: ~6,300 Robux. Target attach rate: 4–7% of DAU.

HUD elements (always visible)

• Cash counter (top center), Gems (top right)
• DROP button (bottom center, massive, thumb-reach)
• Current object + tier badge (left of drop button)
• Combo counter — scales up with combo, glows at high values

Menus

• Inventory, Upgrades, Shop, Pets, Settings — bottom tab bar
• No nested menus deeper than 2 levels
• Every tab opens in under 150ms

Camera

• Follow mode (default): smooth chase behind the object
• Stationary mode: locked at the top, player watches from above
• Toggle via tap on a camera icon — persists between sessions

In-game social

• Leaderboards: longest distance ever, total rebirths, rarest pet
• Chat announcements: rare variants, mega kills, server boosts, rebirths
• Trading is pets only — objects are progression backbone, trading them breaks economy

Title strategy

Launch as 🏔️ Merge Downhill [UPDATE 3]. The suffix signals activity to players and algorithm. Change it every update — free signal boost.

External funnel

• TikTok: 3 clips/week — "watch this 30s roll", "merged 25 times", "rarest drop"
• Roblox Group: member rewards — joining is a free conversion
• Discord: codes, leaks, bug reports, event announcements
• A/B test icon + thumbnail from day one. On Roblox, the icon is worth more than any feature.

Stack

• Language: Luau, strict mode (--!strict)
• Framework: Knit or lightweight in-house service/controller pattern
• Data: ProfileService (session locking mandatory)
• Networking: RemoteEvents for actions; avoid RemoteFunctions in hot paths

Repository structure

src/
├── ReplicatedStorage/Shared/  Config, Types, Util, Remotes
├── ServerScriptService/Services/
│   ├── DataService, EconomyService, DropService
│   ├── MergeService, PetService, ShopService
│   ├── QuestService, AntiExploit
└── StarterPlayer/Controllers/
    ├── DropController, SimulationController (CLIENT physics)
    ├── UIController, CameraController, EffectsController

Required: Hybrid simulation

1. Client simulation, server validation. Each player's object runs on their client. Destruction events are batched and validated server-side against a coarse trajectory model.
2. Per-player obstacle instancing. Each player sees their own obstacles via CollisionGroup + client-only models from a server seed. Zero multi-player physics contention.
3. Debris budget: 60 parts max per client, pooled, despawn after 2.5s with scale-down tween.
4. Object pooling: No Instance.new() in hot paths. Pre-warm: objects 20, debris 80, VFX 40, sounds 30.
5. LOD: Low-poly beyond 400 studs, not rendered beyond 800. Use StreamingEnabled.

Server authority — mandatory

• Client never sends a currency amount — only "I dropped X in lane Y"
• All multipliers read from server-side profile data
• Rate limits: drops 4/s, merges 10/s, purchases 2/s
• Payout sanity-checked against theoretical max. Auto-kick at 10×.

Enforcement: CI check opens the place file and fails the build when budgets are exceeded.

Reference points: Rocket League's clarity, Untitled Goose Game's prop readability, mobile hyper-casual color grading.

Rules

• Silhouette first. Every tier must be identifiable as a black silhouette.
• Escalating visual weight. Tier 25 must look ~50× more imposing than tier 1.
• Destructible = saturated + emissive rim; static = desaturated.
• One accent per world: Farm yellow, Suburbia cyan, Village orange, Forest emerald, City silver.
• Future lighting technology with per-world atmosphere and color correction.

• Screen shake scaled to mass and impact (capped to prevent nausea)
• Hit stop: 40ms freeze on Heavy-class destruction+
• FOV widens 70° → 85° with speed
• Speed lines at screen edge above velocity threshold
• Number pop-ups on every hit, color-coded, pooled
• Coin magnet: cash flies to HUD on an arc with rising pitch
• Drop preview: object hovers, rotates slowly, casts shadow. Anticipation matters.

Ship with master volume + music/SFX split. Game must be fully readable without audio.

Rules

• No text walls — 6 words max per tutorial prompt
• No blocking modals in first 90 seconds
• Skippable, persists
• Instrument every step. If step 3 completion < 85%, the step is broken.

type PlayerProfile = {
    Cash: number, Gems: number, Cores: number,
    CurrentWorld: number,         -- 1..5
    HighestTier: number,          -- 1..25
    Rebirths: number, TotalEarned: number,

    Objects: { [string]: { Tier: number, Variant: string, Count: number } },
    StorageCapacity: number,

    Upgrades: {
        LaunchForce: number, CashMultiplier: number,
        DropSpeed: number, Weight: number,
        ComboWindow: number, MergeLuck: number,
        Storage: number, MagnetRange: number,
    },

    Pets: { [string]: { Id: string, Rarity: string, Mult: number, Golden: boolean } },
    EquippedPets: {string},

    Gamepasses: { [string]: boolean },
    Settings: { CameraMode: string, SFXVolume: number, MusicVolume: number },
    Stats: { TotalDrops: number, TotalSmashed: number, LongestDistance: number },
}

Save on currency change (debounced 30s), merge, purchase, world unlock, rebirth, player leave, and BindToClose. Session locking via ProfileService is mandatory.

Ships with every update, no exceptions

• One new redeemable code (posted to Discord + TikTok same hour)
• At least one new pet — pets are why people read patch notes
• In-game patch notes, not Discord-only
• Refreshed thumbnail (even if just the badge text changes)
• Title suffix incremented: [UPDATE N]
• Performance regression check against budgets before going live
• One fix from the most-repeated review complaint

1. Worlds 4–5ship with 3
2. Tradingdefer
3. Angle controldefer
4. Skyscraper server eventdefer
5. Variants above Golddefer
6. Petsmonetization
7. Rebirthretention
8. Game feelthe product
9. Mobile performance70% of audience
10. Drop → Roll → Smash → Mergethe game

A 10k CCU Roblox game is not the one with more features. It's the one where:

1. 01The first 30 seconds are instantly understandable and immediately satisfying
2. 02Every action produces visible, audible, escalating feedback
3. 03There is always a next goal, visible and reachable within 90 seconds
4. 04It runs at 30 FPS on a cheap Android phone
5. 05It updates every two weeks, forever
6. 06Players record it without being asked

Everything in this document serves those six lines. When a decision is unclear, choose the option that serves them.