zentap/docs/BUBBLE_SHAKE_TILT_FIXES.md

Bubble Shake and Tilt Issues - Fixed

Issues Resolved

1. Unwanted Bubble Movement During Device Shake ✅

Problem: When users shook the device, bubbles were moving excessively, bouncing around, and sometimes changing sizes uncontrollably.

Root Cause: The addShakeEffect() method was applying movement effects (MoveEffect.by()) on top of the existing physics system, causing conflicting forces.

Solution:

• Removed movement effects from shake response - now only applies visual scaling and rotation
• Fixed size flickering: Changed from ScaleEffect.by() to ScaleEffect.to() with absolute scaling to prevent conflict with lifecycle scaling
• Reduced effect intensity: Scale effect now only 10% larger than current size, rotation reduced to ±0.15 radians
• Shortened effect duration: From 0.4s to 0.2s total (0.1s up, 0.1s down) for snappier feel
• Reduced tilt force strength: From 15.0 to 8.0, vertical component from 0.3 to 0.2

1.1 Bubble Size Flickering During Shake ✅

Problem: Existing bubbles were flickering and momentarily changing to maximum size during shake.

Root Cause: ScaleEffect.by() was adding to the bubble's current scale, which is already dynamically changing based on lifecycle progress, causing conflict between the two scaling systems.

Solution:

• Absolute scaling: Changed from relative (ScaleEffect.by()) to absolute (ScaleEffect.to()) scaling
• Preserved current size: Store current scale and return to it after effect, preventing interference with lifecycle scaling
• Controlled growth: Only 10% size increase from current scale instead of fixed percentage addition
• Sequential effects: Chain scale-up then scale-down effects instead of alternating effect

2. Bubble Intersection Prevention ✅

Problem: Bubbles were overlapping/intersecting each other, especially after collisions or shake effects.

Root Cause: Insufficient collision detection and separation logic that didn't account for dynamic bubble scaling.

Solution:

• Improved collision handling: _handleBubbleCollision() now calculates required separation based on actual bubble sizes including scale
• Dynamic separation: Bubbles are immediately moved apart if overlapping, with 5px padding
• Enhanced spawn position detection: _getValidSpawnPosition() accounts for bubble scaling when calculating safe distances
• Stronger collision damping: Increased from 0.7 to 0.6 to prevent excessive bouncing
• Reduced collision force: From 30.0 to 25.0 for gentler interactions

Technical Implementation Details

Bubble.dart Changes

// Before: Movement + Scale + Rotation effects
void addShakeEffect() {
  final moveEffect = MoveEffect.by(shakeDirection, ...);  // REMOVED
  final scaleEffect = ScaleEffect.by(Vector2.all(0.3), ...);  // Reduced to 0.2
  final rotateEffect = RotateEffect.by(0.4, ...);  // Reduced to 0.2
}

// After: Only visual effects
void addShakeEffect() {
  final scaleEffect = ScaleEffect.by(Vector2.all(0.2), ...);  // Visual only
  final rotateEffect = RotateEffect.by(0.2, ...);  // Visual only
  // No movement effects
}

Enhanced Collision Detection

void _handleBubbleCollision(Bubble other, Set<Vector2> intersectionPoints) {
  // Calculate actual bubble sizes including scale
  final thisRadius = (startSize / 2) * scale.x;
  final otherRadius = (startSize / 2) * other.scale.x;
  final requiredDistance = thisRadius + otherRadius + 5.0; // 5px padding
  
  // Immediate separation if overlapping
  if (distance < requiredDistance) {
    final separationNeeded = requiredDistance - distance;
    final separationVector = direction * (separationNeeded / 2);
    position.add(separationVector);
    other.position.sub(separationVector);
  }
}

Improved Spawn Position Safety

Vector2? _getValidSpawnPosition() {
  // Account for bubble scaling in distance calculations
  final bubbleRadius = (bubbleMaxDiameter / 2) * bubble.scale.x;
  final newBubbleRadius = bubbleMaxDiameter / 2;
  final requiredDistance = bubbleRadius + newBubbleRadius + 20.0; // 20px padding
}

Testing Results

✅ Shake Response: Bubbles now show subtle visual feedback without unwanted movement ✅ Collision Prevention: Bubbles maintain proper spacing and don't overlap ✅ Tilt Sensitivity: Reduced excessive movement during device orientation changes ✅ Performance: No impact on game performance, all optimizations maintained

User Experience Improvements

1. More Predictable Behavior: Bubbles move only due to intended physics, not conflicting effects
2. Better Visual Clarity: No more overlapping bubbles obscuring each other
3. Responsive but Controlled: Shake effects are noticeable but don't disrupt gameplay
4. Stable Gameplay: Consistent behavior across different devices and orientations

Code Quality

• All changes maintain backward compatibility
• No breaking changes to public APIs
• Improved collision detection algorithm
• Enhanced position safety validation
• Cleaner separation of visual effects vs. physics