BTD6 on a phone has the same CPU-bound simulation as on PC, with a slower CPU, thermal throttling, and the screen recorder sharing the chip. Late rounds stutter earlier and harder. Cooling, closing apps, lower in-game quality and a lighter defense all help a little; nothing makes round 200 smooth on a phone. Laggy phone recordings can still be cleaned up afterwards.
Why phones struggle sooner
- Same simulation, smaller CPU. The game still moves every bloon and projectile each frame (why that's CPU work). A phone's single-core performance is a fraction of a desktop's.
- Thermal throttling. After a few minutes of sustained load, phones cut clock speed to stay cool. A long freeplay session is exactly that. The game may run fine at round 80 and worse at round 120 for reasons unrelated to the bloons.
- Screen recording shares the chip. iOS and Android screen recorders encode on the same SoC the game is using. The frozen frames you see in the recording are often the game and the recorder fighting for the same cycles.
- Background apps and battery saver. Low-power modes cap performance directly.
What helps
- Turn off battery saver / low power mode before a long session. It's the most common invisible cap.
- Keep the phone cool. Take it out of the case, keep it off soft surfaces, don't charge while playing a long run. Throttling is a bigger factor on phones than any setting.
- Lower in-game graphics quality. On phones the GPU share is less negligible than on PC, so the quality setting helps a bit more here.
- Close other apps, especially anything streaming or syncing.
- Run a lighter defense. The projectile-count rule applies on phones with more force. See towers that cause lag.
- Record at 30 fps if your recorder lets you choose. Fewer frames to encode means less contention with the game.
Cleaning up a laggy phone recording
If you've already recorded a late-round run on your phone and it stutters, the stutter is stored as repeated frames: the recorder wrote the same image several times while the game was stalled (how that happens). Those can be found and removed.
LagCut runs in a desktop browser (Chrome or Edge), so AirDrop or upload the clip to a computer first, trim to the 30 seconds you want, and drop it in. Phone recordings work the same as PC captures as long as the game fills the screen; crop out any system UI first if your recorder included it.