diff --git a/shaders/effects/mosaic.f.glsl b/shaders/effects/mosaic.f.glsl
new file mode 100644
index 0000000..d99af13
--- /dev/null
+++ b/shaders/effects/mosaic.f.glsl
@@ -0,0 +1,70 @@
+/* Copyright (C) 2019 Nunuhara Cabbage <nunuhara@haniwa.technology>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://gnu.org/licenses/>.
+ */
+
+#version 140
+
+uniform sampler2D tex;   // the new scene
+uniform sampler2D old;   // the old scene
+uniform vec2 resolution; // the screen resolution
+uniform float progress;  // effect progress (0..1)
+
+in vec2 tex_coord;
+out vec4 frag_color;
+
+#define MAX_STRIDE 128.0
+
+vec3 get_pixel(vec2 xy) {
+        return mix(texture(old, xy).rgb, texture(tex, xy).rgb, progress);
+}
+
+void main() {
+        // size of each chunk
+        float stride = MAX_STRIDE * (1.0 - abs(progress * 2.0 - 1.0)); // progress=(0..0.5..1) -> stride=(0..max..0)
+        // offset of frag coordinate relative to chunk
+        vec2 offset = mod(gl_FragCoord.xy, stride);
+        // the chunk coordinate
+        vec2 chunk = tex_coord - offset / resolution;
+        // coordinate of chunk center
+        vec2 center = chunk + vec2(stride/2.0, stride/2.0) / resolution;
+
+        // FIXME: In this implementation, the anchor point is at the top left of the screen.
+        //        It should be anchored at the center to match SACT2.dll.
+        frag_color = vec4(get_pixel(center), 1.0);
+}
+
+/* NOTE: This is an alternate implementation which computes an average for each chunk.
+         SACT2.dll does not do this.
+
+#define SAMPLES 8.0
+#define MAX_STRIDE 16.0
+
+vec3 get_pixel(vec2 xy) {
+        return mix(texture(old, xy).xyz, texture(tex, xy).xyz, progress);
+}
+
+void main() {
+        float stride = MAX_STRIDE * (1.0 - abs(progress * 2.0 - 1.0)); // progress=(0..0.5..1) -> stride=(0..max..0)
+        vec3 avg = vec3(0, 0, 0);
+        vec2 xy = floor(gl_FragCoord.xy / (SAMPLES * stride)) * (SAMPLES * stride);
+        for (float j = 0.0; j < SAMPLES; j += 1.0) {
+                for (float i = 0.0; i < SAMPLES; i+= 1.0) {
+                        avg += get_pixel((xy + stride * vec2(i, j)) / resolution);
+                }
+        }
+        avg /= SAMPLES * SAMPLES;
+        frag_color = vec4(avg, 1.0);
+}
+*/
diff --git a/src/effect.c b/src/effect.c
index 71826d1..bfd704b 100644
--- a/src/effect.c
+++ b/src/effect.c
@@ -129,11 +129,13 @@ static void render_effect_shader(struct effect_shader *shader, Texture *old, Tex
 
 #define EFFECT_SHADER(path) { .s = { .prepare = prepare_effect_shader }, .f_path = path}
 static struct effect_shader crossfade_shader = EFFECT_SHADER("shaders/effects/crossfade.f.glsl");
+static struct effect_shader mosaic_shader = EFFECT_SHADER("shaders/effects/mosaic.f.glsl");
 
 extern GLuint main_surface_fb;
 
 static struct effect_shader *effect_shaders[NR_EFFECTS] = {
 	[EFFECT_CROSSFADE] = &crossfade_shader,
+	[EFFECT_CROSSFADE_MOSAIC] = &mosaic_shader,
 };
 
 int sact_Effect(int type, possibly_unused int time, possibly_unused int key)