diff --git a/src/renderer/webgl/shaders/TilemapGPULayer-frag.js b/src/renderer/webgl/shaders/TilemapGPULayer-frag.js
index 862dfd8564..4c9fbf8638 100644
--- a/src/renderer/webgl/shaders/TilemapGPULayer-frag.js
+++ b/src/renderer/webgl/shaders/TilemapGPULayer-frag.js
@@ -5,15 +5,17 @@ module.exports = [
     '#pragma phaserTemplate(features)',
     '#ifdef GL_FRAGMENT_PRECISION_HIGH',
     'precision highp float;',
+    '#define DATA_PRECISION highp',
     '#else',
     'precision mediump float;',
+    '#define DATA_PRECISION mediump',
     '#endif',
     '/* Redefine MAX_ANIM_FRAMES to support animations with different frame numbers. */',
     '#define MAX_ANIM_FRAMES 0',
     '#pragma phaserTemplate(fragmentDefine)',
     'uniform vec2 uResolution;',
     'uniform sampler2D uMainSampler;',
-    'uniform sampler2D uLayerSampler;',
+    'uniform DATA_PRECISION sampler2D uLayerSampler;',
     'uniform vec2 uMainResolution;',
     'uniform vec2 uLayerResolution;',
     'uniform float uTileColumns;',
@@ -21,7 +23,7 @@ module.exports = [
     'uniform float uAlpha;',
     'uniform float uTime;',
     '#if MAX_ANIM_FRAMES > 0',
-    'uniform sampler2D uAnimSampler;',
+    'uniform DATA_PRECISION sampler2D uAnimSampler;',
     'uniform vec2 uAnimResolution;',
     '#endif',
     'varying vec2 outTexCoord;',
@@ -31,9 +33,14 @@ module.exports = [
     '{',
     '    return uMainResolution;',
     '}',
+    'vec4 texelBytes (vec4 texel)',
+    '{',
+    '    return floor(texel * 255.0 + 0.5);',
+    '}',
     'float floatTexel (vec4 texel)',
     '{',
-    '    return texel.r * 255.0 + (texel.g * 255.0 * 256.0) + (texel.b * 255.0 * 256.0 * 256.0) + (texel.a * 255.0 * 256.0 * 256.0 * 256.0);',
+    '    vec4 bytes = texelBytes(texel);',
+    '    return bytes.r + (bytes.g * 256.0) + (bytes.b * 256.0 * 256.0) + (bytes.a * 256.0 * 256.0 * 256.0);',
     '}',
     'struct Tile',
     '{',
@@ -50,7 +57,7 @@ module.exports = [
     '    vec2 tile = floor(texelCoord);',
     '    vec2 uv = fract(texelCoord);',
     '    uv.y = 1.0 - uv.y;',
-    '    vec4 texel = texture2D(uLayerSampler, (tile + 0.5) / uLayerResolution) * 255.0;',
+    '    vec4 texel = texelBytes(texture2D(uLayerSampler, (tile + 0.5) / uLayerResolution));',
     '    float flags = texel.a;',
     '    /* Check for empty tile flag in bit 28. */',
     '    if (flags == 16.0)',
diff --git a/src/renderer/webgl/shaders/src/TilemapGPULayer.frag b/src/renderer/webgl/shaders/src/TilemapGPULayer.frag
index 8430963a03..a369a796fd 100644
--- a/src/renderer/webgl/shaders/src/TilemapGPULayer.frag
+++ b/src/renderer/webgl/shaders/src/TilemapGPULayer.frag
@@ -7,8 +7,10 @@
 
 #ifdef GL_FRAGMENT_PRECISION_HIGH
 precision highp float;
+#define DATA_PRECISION highp
 #else
 precision mediump float;
+#define DATA_PRECISION mediump
 #endif
 
 /* Redefine MAX_ANIM_FRAMES to support animations with different frame numbers. */
@@ -18,7 +20,16 @@ precision mediump float;
 
 uniform vec2 uResolution;
 uniform sampler2D uMainSampler;
-uniform sampler2D uLayerSampler;
+// The layer and animation samplers carry packed integer data (tile indices and
+// flag bits), not colour, so they need more than the default sampler precision.
+// GLSL ES 1.00 declares fragment shader samplers `lowp` by default (spec 4.5.3),
+// which only guarantees 8-bit absolute precision. A driver that takes that
+// literally decodes the layer texel a fraction below its true byte value, which
+// is enough to break the exact comparisons that read the flag bits out of it.
+// Observed on Adreno 740/750 (Galaxy S23 / S23 Ultra / Z Fold 7), where every
+// empty tile failed its `flags == 16.0` test and drew tile 0 of the tileset over
+// the layers beneath it.
+uniform DATA_PRECISION sampler2D uLayerSampler;
 uniform vec2 uMainResolution;
 uniform vec2 uLayerResolution;
 uniform float uTileColumns;
@@ -27,7 +38,7 @@ uniform float uAlpha;
 uniform float uTime;
 
 #if MAX_ANIM_FRAMES > 0
-uniform sampler2D uAnimSampler;
+uniform DATA_PRECISION sampler2D uAnimSampler;
 uniform vec2 uAnimResolution;
 #endif
 
@@ -42,10 +53,20 @@ vec2 getTexRes ()
     return uMainResolution;
 }
 
+// Snap a UNORM8 texel back to the exact 0-255 byte values it was uploaded with.
+// The channels below are weighted by powers of 256, so a fetch that is off by a
+// fraction of a byte becomes an error of hundreds in the decoded value.
+vec4 texelBytes (vec4 texel)
+{
+    return floor(texel * 255.0 + 0.5);
+}
+
 // Convert a vec4 texel to a float.
 float floatTexel (vec4 texel)
 {
-    return texel.r * 255.0 + (texel.g * 255.0 * 256.0) + (texel.b * 255.0 * 256.0 * 256.0) + (texel.a * 255.0 * 256.0 * 256.0 * 256.0);
+    vec4 bytes = texelBytes(texel);
+
+    return bytes.r + (bytes.g * 256.0) + (bytes.b * 256.0 * 256.0) + (bytes.a * 256.0 * 256.0 * 256.0);
 }
 
 struct Tile
@@ -67,7 +88,7 @@ Tile getLayerData (vec2 coord)
     // Invert Y, as textures are flipped in GL.
     uv.y = 1.0 - uv.y;
 
-    vec4 texel = texture2D(uLayerSampler, (tile + 0.5) / uLayerResolution) * 255.0;
+    vec4 texel = texelBytes(texture2D(uLayerSampler, (tile + 0.5) / uLayerResolution));
 
     float flags = texel.a;