diff --git a/include/gfx/gfx.h b/include/gfx/gfx.h
index 8e7ffd2..3e36c26 100644
--- a/include/gfx/gfx.h
+++ b/include/gfx/gfx.h
@@ -127,6 +127,9 @@ void gfx_blend_screen_alpha(Texture *dst, int dx, int dy, Texture *src, int sx,
 void gfx_fill(struct texture *dst, int x, int y, int w, int h, int r, int g, int b);
 void gfx_fill_alpha_color(struct texture *dst, int x, int y, int w, int h, int r, int g, int b, int a);
 void gfx_fill_amap(struct texture *dst, int x, int y, int w, int h, int a);
+void gfx_fill_amap_over_border(Texture *dst, int x, int y, int w, int h, int alpha, int border);
+void gfx_fill_amap_under_border(Texture *dst, int x, int y, int w, int h, int alpha, int border);
+void gfx_fill_amap_gradation_ud(Texture *dst, int x, int y, int w, int h, int up_a, int down_a);
 void gfx_add_da_daxsa(struct texture *dst, int dx, int dy, struct texture *src, int sx, int sy, int w, int h);
 void gfx_blend_da_daxsa(struct texture *dst, int dx, int dy, struct texture *src, int sx, int sy, int w, int h);
 void gfx_sub_da_daxsa(struct texture *dst, int dx, int dy, struct texture *src, int sx, int sy, int w, int h);
@@ -139,8 +142,6 @@ void gfx_copy_rot_zoom_amap(Texture *dst, Texture *src, int sx, int sy, int w, i
 void gfx_copy_rot_zoom_use_amap(Texture *dst, Texture *src, int sx, int sy, int w, int h, float rotate, float mag);
 void gfx_copy_reverse_LR(Texture *dst, int dx, int dy, Texture *src, int sx, int sy, int w, int h);
 void gfx_copy_reverse_amap_LR(Texture *dst, int dx, int dy, Texture *src, int sx, int sy, int w, int h);
-void gfx_fill_amap_over_border(Texture *dst, int x, int y, int w, int h, int alpha, int border);
-void gfx_fill_amap_under_border(Texture *dst, int x, int y, int w, int h, int alpha, int border);
 void gfx_copy_rotate_y(Texture *dst, Texture *front, Texture *back, int sx, int sy, int w, int h, float rot, float mag);
 void gfx_copy_rotate_y_use_amap(Texture *dst, Texture *front, Texture *back, int sx, int sy, int w, int h, float rot, float mag);
 void gfx_copy_rotate_x(Texture *dst, Texture *front, Texture *back, int sx, int sy, int w, int h, float rot, float mag);
diff --git a/shaders/fill_amap_gradation_ud.f.glsl b/shaders/fill_amap_gradation_ud.f.glsl
new file mode 100644
index 0000000..15ec654
--- /dev/null
+++ b/shaders/fill_amap_gradation_ud.f.glsl
@@ -0,0 +1,27 @@
+/* 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/>.
+ */
+
+uniform sampler2D tex;
+uniform float threshold;
+uniform float threshold2;
+
+in vec2 tex_coord;
+out vec4 frag_color;
+
+void main() {
+	float rate = threshold + (threshold2 - threshold) * tex_coord.y;
+	frag_color = vec4(texture(tex, tex_coord).rgb, rate);
+}
diff --git a/src/draw.c b/src/draw.c
index b7a4e0e..0221024 100644
--- a/src/draw.c
+++ b/src/draw.c
@@ -34,6 +34,7 @@ struct copy_shader {
 	// optional
 	GLint color;
 	GLint threshold;
+	GLint threshold2;
 };
 
 struct copy_data {
@@ -43,6 +44,7 @@ struct copy_data {
 	// optional
 	float r, g, b, a;
 	float threshold;
+	float threshold2;
 };
 
 #define ROTATE_DATA(dst, _sx, _sy, _w, _h)		\
@@ -68,6 +70,7 @@ static struct copy_shader blend_use_amap_color_shader;
 static struct copy_shader fill_shader;
 static struct copy_shader fill_amap_over_border_shader;
 static struct copy_shader fill_amap_under_border_shader;
+static struct copy_shader fill_amap_gradation_ud_shader;
 static struct copy_shader hitbox_shader;
 static struct copy_shader hitbox_noblend_shader;
 static struct copy_shader dilate_shader;
@@ -81,6 +84,7 @@ static void prepare_copy_shader(struct gfx_render_job *job, void *data)
 
 	glUniform4f(s->color, d->r, d->g, d->b, d->a);
 	glUniform1f(s->threshold, d->threshold);
+	glUniform1f(s->threshold2, d->threshold2);
 }
 
 static void load_copy_shader(struct copy_shader *s, const char *v_path, const char *f_path)
@@ -90,6 +94,7 @@ static void load_copy_shader(struct copy_shader *s, const char *v_path, const ch
 	s->top_right = glGetUniformLocation(s->s.program, "top_right");
 	s->color = glGetUniformLocation(s->s.program, "color");
 	s->threshold = glGetUniformLocation(s->s.program, "threshold");
+	s->threshold2 = glGetUniformLocation(s->s.program, "threshold2");
 	s->s.prepare = prepare_copy_shader;
 }
 
@@ -131,6 +136,9 @@ void gfx_draw_init(void)
 	// fill shader that only fills fragments below a certain alpha threshold
 	load_copy_shader(&fill_amap_under_border_shader, "shaders/render.v.glsl", "shaders/fill_amap_under_border.f.glsl");
 
+	// fill shader that fills the alpha map with a gradient
+	load_copy_shader(&fill_amap_gradation_ud_shader, "shaders/render.v.glsl", "shaders/fill_amap_gradation_ud.f.glsl");
+
 	// shader that discards texels that fail a hitbox test
 	load_copy_shader(&hitbox_shader, "shaders/render.v.glsl", "shaders/hitbox.f.glsl");
 
@@ -541,6 +549,18 @@ void gfx_fill_amap_under_border(Texture *dst, int x, int y, int w, int h, int al
 	restore_blend_mode();
 }
 
+void gfx_fill_amap_gradation_ud(Texture *dst, int x, int y, int w, int h, int up_a, int down_a)
+{
+	glBlendFuncSeparate(GL_ZERO, GL_ONE, GL_ONE, GL_ZERO);
+
+	struct copy_data data = COPY_DATA(x, y, 0, 0, w, h);
+	data.threshold = up_a / 255.0;
+	data.threshold2 = down_a / 255.0;
+	run_fill_shader(&fill_amap_gradation_ud_shader.s, dst, &data);
+
+	restore_blend_mode();
+}
+
 void gfx_add_da_daxsa(Texture *dst, int dx, int dy, Texture *src, int sx, int sy, int w, int h)
 {
 	// color = dst_color
diff --git a/src/hll/DrawGraph.c b/src/hll/DrawGraph.c
index 16780f4..5683dfc 100644
--- a/src/hll/DrawGraph.c
+++ b/src/hll/DrawGraph.c
@@ -176,7 +176,11 @@ static void DrawGraph_FillAMapUnderBorder(int dst, int x, int y, int w, int h, i
 	gfx_fill_amap_under_border(DTEX(dst), x, y, w, h, alpha, border);
 }
 
-//void DrawGraph_FillAMapGradationUD(int dst, int x, int y, int w, int h, int up_a, int down_a);
+static void DrawGraph_FillAMapGradationUD(int dst, int x, int y, int w, int h, int up_a, int down_a)
+{
+	gfx_fill_amap_gradation_ud(DTEX(dst), x, y, w, h, up_a, down_a);
+}
+
 //void DrawGraph_FillScreen(int dst, int x, int y, int w, int h, int r, int g, int b);
 //void DrawGraph_FillMultiply(int dst, int x, int y, int w, int h, int r, int g, int b);
 //void DrawGraph_SaturDP_DPxSA(int dst, int dx, int dy, int src, int sx, int sy, int w, int h);
@@ -405,7 +409,7 @@ HLL_LIBRARY(DrawGraph,
 	    HLL_EXPORT(FillAMap, DrawGraph_FillAMap),
 	    HLL_EXPORT(FillAMapOverBorder, DrawGraph_FillAMapOverBorder),
 	    HLL_EXPORT(FillAMapUnderBorder, DrawGraph_FillAMapUnderBorder),
-	    //HLL_EXPORT(FillAMapGradationUD, DrawGraph_FillAMapGradationUD),
+	    HLL_EXPORT(FillAMapGradationUD, DrawGraph_FillAMapGradationUD),
 	    //HLL_EXPORT(FillScreen, DrawGraph_FillScreen),
 	    //HLL_EXPORT(FillMultiply, DrawGraph_FillMultiply),
 	    //HLL_EXPORT(SaturDP_DPxSA, DrawGraph_SaturDP_DPxSA),