You’re building a tight Flappy Bird loop for phones: tap-to-flap, gravity, pipes, scoring, and a clean fail state. This is a fast prototype path you can use before rebuilding in Unity or ship if performance fits.
Goal and immediate implementation: create a global variable named BirdYVel (number). Add these exact events in the Game scene:
1) At the beginning of the scene → Do = 0 to the variable BirdYVel.
2) If Touch or mouse button is pressed → Do = -380 to BirdYVel and Change animation of Bird to “Flap”.
3) Each frame → Do + (1200 * TimeDelta()) to BirdYVel.
4) Each frame → Set Y position of Bird to Bird.Y() + (BirdYVel * TimeDelta()).
5) Each frame → If BirdYVel > 900 then Do = 900 to BirdYVel.
Those numbers tune flap strength and gravity; TimeDelta() keeps physics consistent across 60/90/120Hz devices. Here “no code” means building logic as events in the event system instead of writing C# or JavaScript.
Mobile constraints matter: pick a base resolution, anchor UI for notches, limit draw calls and memory, and test on-device each time you tweak physics. Later sections cover pipe spawning, scoring checkpoints, collision masks, and export options.
Author: George Jones — this is a practical, developer-focused route to quick iteration and real on-device validation for PlayMobile.online readers.
Build the core Flap + Gravity loop in the event system
The feel of your bird comes from a tuned flap impulse and frame-rate‑safe gravity. Keep control of vertical velocity with a single global variable and organize events into clear groups: input, physics integration, and animation state.
Create the Bird sprite and collision settings
Create a Sprite with two animations: Idle and Flap. Disable platformer behavior so you control Y velocity directly.
Set origin to center, keep sprite size readable on a 6‑inch screen (about 64–128px tall), and edit the collision mask to be tight (manual points or automatic then trim).
Event sheet: input, physics, and clamp
- Input group: Condition — Touch or Mouse OR combined condition; Action — Do = -380 to variable BirdYVel and Change animation of Bird to “Flap”. Gate with a short variable cooldown if needed.
- Physics group (each frame): Do + (1200 * TimeDelta()) to BirdYVel; Set Y position to Bird.Y() + (BirdYVel * TimeDelta()).
- Clamp group: If BirdYVel > 900 → Do = 900 to BirdYVel (prevents tunneling on high refresh).
| Item | Value | Why it matters |
|---|---|---|
| Flap impulse | -380 | Gives quick upward peak; tune for less twitch. |
| Gravity | 1200 | Delta-time stable fall; increase if it floats. |
| Max fall | 900 | Prevents collision skipping on 90–120Hz panels. |
| Collision mask | Tight polygon | Reduces false hits and reads on small screens. |
Testing workflow: change one number, export to a low-end Android device, and iterate. If the bird floats, raise gravity; if it jerks, lower the flap impulse or add a 100–200ms input cooldown. This approach mirrors using Time.deltaTime in Unity for crisp arcade mechanics and helps you prototype reliable mechanics in the event-driven system.
Project setup for a mobile-first Flappy Bird clone
Begin by choosing a consistent portrait canvas so play feels identical across modern US phones. Use 720×1280 as a baseline and set scaling to fit height with letterbox or viewport cropping. That keeps pipe gap and touch areas consistent on tall iPhones and wider Android platforms.
Safe areas and UI anchors
Anchor the score to top-center. Place pause and mute at the top-left/right with a 24–40px safe margin to avoid notches and rounded corners. Test on devices with different safe areas so HUD spacing never overlaps the display cutout.
Scene and variable structure
- Boot scene: init global vars (best score, audio, difficulty) and route to Menu.
- Menu: asset loading and options UI.
- Game: runtime objects, scene vars (current score, pipe timer).
- Game Over: results and restart flow.
| Item | Setting | Why it matters |
|---|---|---|
| Base res | 720×1280 | Keeps physics and gap consistent |
| UI anchors | Top-center / safe margins | Prevents notch collisions |
| Assets | Scaled for target res | Reduces memory and draw calls |
Use global vars for persistent state and scene vars for run-specific values. Iterate fast: change one setting, export a quick build, and test on a real phone to verify touch feel and frame pacing.
Build pipes and scoring with the event system
Spawn logic and a reliable checkpoint are the heartbeat of the obstacle flow. Use a grouped pipe set so top, bottom, and checkpoint stay aligned. That keeps collision and scoring predictable across devices.
Spawn and move pipes
Create a scene timer named “PipeSpawn”. If Timer “PipeSpawn” > SpawnInterval → reset timer and Create TopPipe, BottomPipe, Checkpoint at X just past the right edge. Apply RandomInRange(MinY, MaxY) to the pair’s Y, then clamp so gaps never spawn off-screen.
Move pipes each frame with TimeDelta(): Pipe.X() = Pipe.X() – PipeSpeed * TimeDelta(). Constant-speed movement feels fairer than frame-based deltas and keeps mechanics stable across refresh rates.
Scoring and cleanup
Use an invisible Checkpoint centered in the gap. Event: If Bird collides with Checkpoint AND Checkpoint.Variable(scored) = 0 → Add 1 to Score; Do = 1 to Checkpoint.Variable(scored); Play sound. This “do once” pattern prevents double counts when overlap lasts multiple frames.
Delete pipes and checkpoints when X < -pipeWidth. Long runs will hitch on low-end Android if you forget cleanup; consider pooling when spawn rate rises.
| Item | Event / Action | Why it matters |
|---|---|---|
| Spawn timer | Reset Timer “PipeSpawn”, Create pipe pair | Keeps rhythm and controllable difficulty |
| Checkpoint | On collision, check scored flag then add score | Prevents double-counting across frames |
| Pipe movement | Subtract PipeSpeed * TimeDelta() | Frame-rate stable motion for fair play |
| Cleanup / pooling | Delete when off-screen or reuse | Controls memory and reduces hitches on weaker devices |
Scrolling background and ground that won’t drain battery
Keep the backdrop light: two sprites and a single wrap check is enough for endless scroll. This approach reduces draw calls and keeps battery use low on older phones.
Infinite scrolling with two sprites
Place two background sprites on a background layer. Move both left at BgSpeed * TimeDelta().
When one sprite’s X is
Parallax option
Add a far layer only if you need depth. Move it at 30–50% of the main speed to get parallax without extra shaders or heavy effects.
Ground and safe hitboxes
Use a single ground object with a stable polygon mask. Avoid many jagged points that behave differently across resolutions.
Make hitboxes slightly forgiving for small screens. A small buffer reduces frustration for the player while keeping core mechanics fair.
| Feature | Implementation | Benefit |
|---|---|---|
| Background wrap | Two sprites + wrap check | Low draw calls, battery friendly |
| Parallax | 30–50% speed far layer | Depth with minimal cost |
| Ground collision | Single sprite, tight mask | Consistent hits across devices |
Mobile performance checks you should do before you export
Run simple checks on phones to catch the slowdowns that never show in the editor. Test on at least one low-end Android and one mid-range device so you see fill-rate and memory constraints early.
What to measure and why
Profile object counts during a 2–3 minute play session. Watch FPS and note spikes right after pipes spawn. If you see stutters, that points to creation costs or large textures.
Practical fixes
- Draw calls: reduce layers (background, gameplay, UI) and reuse the same pipe sprite set to enable batching.
- Memory: constrain texture sizes and compress audio to keep APK/AAB size down and reduce load times.
- Battery: cap frame rate if you don’t need 120 FPS and avoid always-on particle effects to limit heat and drain.
- Runtime cleanup: use pooling when spawn rate rises so you reuse pipes instead of creating/destroying objects every time.
| Check | Action | Why it matters |
|---|---|---|
| FPS stability | Profile on-device for 2–3 minutes | Reveals spikes from spawns or large asset loads |
| Draw calls | Limit layers, reuse sprites, avoid post effects | Reduces GPU load on weak platforms |
| Memory | Resize textures, compress audio, trim atlases | Prevents OOM crashes and long load times |
| Battery & heat | Cap frame rate, limit overdraw, remove constant particles | Keeps play sessions longer and devices cooler |
Also test at realistic screen scales. High resolutions increase fill-rate cost, so validate on budget devices rather than only on flagship hardware. For diagnosing lag, follow the engine’s “Intro: Optimization” video, then export a short test build and iterate.
Beginner mistakes that break Flappy Bird clones (and quick fixes)
Small bugs on real devices often reveal flaws your editor never showed. Focus on input, scoring, collisions, and spawn ranges so your build survives varied phones and browsers. Use the event system to gate behavior and expose a few debug vars while you tune.
Input conflicts
Some devices fire touch and mouse paths together. That makes the bird jump twice.
Fix: use one unified input condition or set a JustFlapped boolean and reset it with a 100–200 ms timer. This prevents duplicate triggers across browsers and touch layers.
Score bugs
Overlaps can add points across frames. Add a Checkpoint variable named scored and require scored=0 before adding score. Then set scored=1 immediately.
Collision and gap issues
Automatic masks can be oversized. Edit the collision polygon in the sprite editor and test on different aspect ratios.
If scaling changes world size, define a stable virtual resolution and clamp pipe Y with explicit min/max derived from screen height so gaps never spawn off-screen.
| Issue | Symptom | Quick fix |
|---|---|---|
| Input conflicts | Double taps / duplicate flaps | Unified input event or JustFlapped timer/boolean |
| Score overlap | Multiple points per passage | Checkpoint.variable(scored)=0 check, then set to 1 |
| Collision mask | False hits | Edit polygon, test on target resolutions |
| Difficulty spikes | Impossible gaps | Clamp RandomInRange with min/max based on gap size |
Use official GDevelop learning resources and proven industry practice
Trust the academy material and production practices to move from prototype to build. When you follow official guides you skip trial-and-error and fix issues faster on target platforms.
Follow these focused resources to solve specific problems in this project:
- The Events — structure your event sheets and reduce logic bugs (best for input and scoring).
- In Depth Sprite — tighten collision masks and set animation frames correctly for the bird.
- Expression Builder — build score UI expressions fast and avoid update errors.
- Exporting Your Game & Intro: Optimization — packaging settings and the first stop when a build stutters.
Map lessons to issues: use Timers and Waiting for spawn rhythm, Intermediate Touchscreen Controls for anchors, and Troubleshooting Tools when collisions behave oddly. These video and written resources act as tools for reliable development.
If you plan to move engines, scan Unity Manual — Visual Scripting. Its nodes/graphs map closely to event conditions/actions so you can transfer concepts smoothly.
| Resource | Problem | Benefit |
|---|---|---|
| The Events | Confused logic or double input | Clear condition → action flow |
| In Depth Sprite | False collisions | Tighter masks, consistent hits |
| Intro: Optimization | Stutter on low-end phones | Prioritized fixes: textures, draw calls |
Follow the rapid prototyping loop — build → test on device → tweak — and rely on official resources over random forum snippets. This keeps your iterations fast and your releases stable for players and developers alike.
Export and publish to Android and iOS with the right settings
Finalizing your build means choosing the right export path and testing on real devices. Pick the mobile-optimized export flow in your engine and generate an Android App Bundle (AAB) for the Play Store. The AAB improves delivery and is now preferred over old APK workflows.
Store-facing options and runtime settings
Set all store assets before you export. Fill icon sizes, splash images, and the app name so your US storefront listing looks professional.
Lock orientation to portrait, enable safe-area handling, and choose scaling that preserves gameplay across iPhones and Android devices. These options prevent HUDs from sitting under notches.
Simple device matrix and QA checklist
| Device | What to test | Key watch-outs |
|---|---|---|
| Low-end Android | Long run memory & frame pacing | Memory spikes, texture size |
| Mid-range Android | Typical user performance | Draw calls, battery heat |
| iPhone (modern) | Touch feel & safe areas | Touch latency, notch overlap |
What to watch and how to iterate
During testing watch touch latency, collision fairness, frame pacing, and memory growth over 3–5 minute runs. Keep versioning steady and test the same run length each build so you can measure regressions.
If low-end performance fails, reduce texture sizes, simplify layers and effects, and implement pooling for repeated objects. Exporting and publishing is settings and QA—so you can finish this without writing a single line code.
Conclusion
Conclude with a focused checklist that turns a prototype into a ship-ready build. You now have a manual Bird velocity plus delta-time gravity, capped fall speed, timer-based pipe spawning with cleanup, checkpoint scoring, and a Menu → Game → Game Over flow.
Keep mobile constraints central: stable scaling across screen sizes, anchored UI for notches, and tight collision masks so the pipe gap reads fair on all platforms.
Prioritize performance: limit draw calls and layers, keep textures reasonable, delete or pool pipes, and cap frame rate if heat or battery rise. Fix common bugs early—unified touch input, scored=true flags on checkpoints, and clamped pipe Y ranges.
Next steps: add pause and best-score save, export an AAB and run your device matrix, then change one tuning variable per build. Use the official Academy and Unity Visual Scripting docs if you port the loop to another engine. Ship only when the feel matches on real devices, not just in the editor.
