diff --git a/modules/NIGHTDLL/nt_msg.c b/modules/NIGHTDLL/nt_msg.c
index 9e44fb0..5e626fb 100644
--- a/modules/NIGHTDLL/nt_msg.c
+++ b/modules/NIGHTDLL/nt_msg.c
@@ -7,7 +7,6 @@
 
 #include "portab.h"
 #include "system.h"
-#include "sdl_core.h"
 #include "utfsjis.h"
 #include "ags.h"
 #include "nact.h"
@@ -236,7 +235,7 @@ static void ntmsg_out(int wNum, int wSize, int wColorR, int wColorG, int wColorB
 		char mbuf[20];
 		int cw, delta, wcnt;
 		
-		wcnt = sdl_getTicks();
+		wcnt = sys_get_ticks();
 		
 		mbuf[0] = '\0';
 		msg = get_char(msg, mbuf, sizeof(mbuf) -1); 
@@ -267,7 +266,7 @@ static void ntmsg_out(int wNum, int wSize, int wColorR, int wColorG, int wColorB
 			needupdate = false;
 			
 			// keywait
-			delta = sdl_getTicks() - wcnt;
+			delta = sys_get_ticks() - wcnt;
 			if (delta < wSpeed) {
 				if (sys_keywait(wSpeed - delta, KEYWAIT_NONCANCELABLE)) {
 					
@@ -311,14 +310,14 @@ static int ntmsg_keywait() {
 	night.waitkey = -1;
 	
 	while (night.waitkey == -1 && !nact->is_quit) {
-		int st = sdl_getTicks();
+		int st = sys_get_ticks();
 		int interval = 25;
 		
 		if (!night.zhiding) {
 			interval = night.sp[SPNO_MSG_KEYANIM]->u.anime.interval;
 			hakanim(i++);
 		} 
-		sys_keywait(interval - (sdl_getTicks() - st), KEYWAIT_NONCANCELABLE);
+		sys_keywait(interval - (sys_get_ticks() - st), KEYWAIT_NONCANCELABLE);
 	}
 	
 	night.waittype = KEYWAIT_NONE;
diff --git a/modules/NIGHTDLL/sprite_eupdate.c b/modules/NIGHTDLL/sprite_eupdate.c
index ea52cb5..a006c89 100644
--- a/modules/NIGHTDLL/sprite_eupdate.c
+++ b/modules/NIGHTDLL/sprite_eupdate.c
@@ -30,7 +30,6 @@
 #include "sprite.h"
 #include "gfx.h"
 #include "effect.h"
-#include "sdl_core.h"
 
 /*
   効果つき画面更新
@@ -55,12 +54,12 @@ void nt_sp_eupdate(int no, int time, int cancel) {
 	struct effect *eff = effect_init(&rect, NULL, 0, 0, gfx_getDIB(), 0, 0, type);
 
 	int sttime, curtime;
-	sttime = curtime = sdl_getTicks();
+	sttime = curtime = sys_get_ticks();
 	int edtime = curtime + time;
 
-	while ((curtime = sdl_getTicks()) < edtime) {
+	while ((curtime = sys_get_ticks()) < edtime) {
 		effect_step(eff, (float)(curtime - sttime) / (edtime - sttime));
-		int rest = 16 - (sdl_getTicks() - curtime);
+		int rest = 16 - (sys_get_ticks() - curtime);
 		int key = sys_keywait(rest, cancel ? KEYWAIT_CANCELABLE : KEYWAIT_NONCANCELABLE);
 		if (cancel && key)
 			break;
diff --git a/modules/NightDemonDemo/NightDemonDemo.c b/modules/NightDemonDemo/NightDemonDemo.c
index ed831c5..9a0e1c8 100644
--- a/modules/NightDemonDemo/NightDemonDemo.c
+++ b/modules/NightDemonDemo/NightDemonDemo.c
@@ -33,7 +33,6 @@
 #include "alk.h"
 #include "music.h"
 #include "gfx.h"
-#include "sdl_core.h"
 #include "input.h"
 #include "cg.h"
 #include "jpeg.h"
@@ -53,9 +52,9 @@ static void ndd_run(int demonum) {
 	if (mus)
 		musbgm_play(mus, 0, 100, 0);
 
-	uint32_t start = sdl_getTicks();
+	uint32_t start = sys_get_ticks();
 	while (!nact->is_quit) {
-		int i = (sdl_getTicks() - start) / (1000 / FPS);
+		int i = (sys_get_ticks() - start) / (1000 / FPS);
 		if (i >= alk->datanum)
 			break;
 
@@ -70,7 +69,7 @@ static void ndd_run(int demonum) {
 			WARNING("Cannot decode CG %d in %s", i, alk_path);
 		}
 
-		int wait_ms = (i + 1) * (1000 / FPS) - (sdl_getTicks() - start);
+		int wait_ms = (i + 1) * (1000 / FPS) - (sys_get_ticks() - start);
 		if (wait_ms > 0) {
 			if (sys_keywait(wait_ms, KEYWAIT_CANCELABLE))
 				break;
diff --git a/modules/SACT/screen_quake.c b/modules/SACT/screen_quake.c
index abd3dec..e584fb5 100644
--- a/modules/SACT/screen_quake.c
+++ b/modules/SACT/screen_quake.c
@@ -34,7 +34,6 @@
 #include "input.h"
 #include "sact.h"
 #include "sprite.h"
-#include "sdl_core.h"
 #include "randMT.h"
 
 #define M_PIf ((float)M_PI)
@@ -78,9 +77,9 @@ void sp_quake_screen(int type, int p1, int p2, int time, int cancel) {
 	
 	if (type > 1) return;
 	
-	sttime = sdl_getTicks();
+	sttime = sys_get_ticks();
 	edtime = time * 10 + sttime;
-	while ((curtime = sdl_getTicks()) < edtime) {
+	while ((curtime = sys_get_ticks()) < edtime) {
 		int adjx, adjy;
 		
 		cb[type]((float)(curtime - sttime)/(edtime - sttime), p1, p2, &adjx, &adjy);
diff --git a/modules/SACT/sprite_anime.c b/modules/SACT/sprite_anime.c
index f9d3f2e..658de2a 100644
--- a/modules/SACT/sprite_anime.c
+++ b/modules/SACT/sprite_anime.c
@@ -28,7 +28,6 @@
 #include "portab.h"
 #include "system.h"
 #include "ags.h"
-#include "sdl_core.h"
 #include "sact.h"
 #include "sprite.h"
 
@@ -44,7 +43,7 @@ static int eventCB_ANIM(sprite_t *sp, agsevent_t *e) {
 	if (e->type != AGSEVENT_TIMER) return 0;
 	
 	// 現在時刻の取得
-	now = sdl_getTicks();
+	now = sys_get_ticks();
 	
 	// 指定時間までスキップ
 	if ((now - sp->u.anime.starttime) < sp->u.anime.interval) return 0;
@@ -85,7 +84,7 @@ void sp_anime_setup(sprite_t *sp) {
 	int n = 0;
 	
 	sp->u.anime.interval = 500; // デフォルトの間隔 0.5秒
-	sp->u.anime.starttime = sdl_getTicks(); // 開始時刻
+	sp->u.anime.starttime = sys_get_ticks(); // 開始時刻
 	sp->u.anime.tick = 0;      // カウンタ初期化
 	
 	// アニメパターンはいくつあるか
diff --git a/modules/SACT/sprite_eupdate.c b/modules/SACT/sprite_eupdate.c
index dcd65f3..7d5156e 100644
--- a/modules/SACT/sprite_eupdate.c
+++ b/modules/SACT/sprite_eupdate.c
@@ -31,7 +31,6 @@
 #include "sprite.h"
 #include "gfx.h"
 #include "effect.h"
-#include "sdl_core.h"
 
 /*
   効果つき画面更新
@@ -56,12 +55,12 @@ void sp_eupdate(int type, int time, int cancel) {
 	struct effect *eff = effect_init(&rect, NULL, 0, 0, gfx_getDIB(), 0, 0, effect);
 
 	int sttime, curtime;
-	sttime = curtime = sdl_getTicks();
+	sttime = curtime = sys_get_ticks();
 	int edtime = curtime + time * 10;
 
-	while ((curtime = sdl_getTicks()) < edtime) {
+	while ((curtime = sys_get_ticks()) < edtime) {
 		effect_step(eff, (float)(curtime - sttime) / (edtime - sttime));
-		int rest = 16 - (sdl_getTicks() - curtime);
+		int rest = 16 - (sys_get_ticks() - curtime);
 		int key = sys_keywait(rest, cancel ? KEYWAIT_CANCELABLE : KEYWAIT_NONCANCELABLE);
 		if (cancel && key)
 			break;
diff --git a/modules/SACT/sprite_event.c b/modules/SACT/sprite_event.c
index 16d1ae2..5003adf 100644
--- a/modules/SACT/sprite_event.c
+++ b/modules/SACT/sprite_event.c
@@ -30,7 +30,6 @@
 
 #include "portab.h"
 #include "system.h"
-#include "sdl_core.h"
 #include "menu.h"
 #include "input.h"
 #include "nact.h"
@@ -213,7 +212,7 @@ static void cb_waitkey_simple(agsevent_t *e) {
 	switch (e->type) {
 	case AGSEVENT_KEY_PRESS:
 		if (e->code == KEY_Z) {
-			cur = sdl_getTicks();
+			cur = sys_get_ticks();
 			if (!sact.zhiding) {
 				slist_foreach(sact.sp_zhide, cb_defocused_zkey, &update);
 				sact.zhiding = true;
@@ -243,7 +242,7 @@ static void cb_waitkey_simple(agsevent_t *e) {
 	case AGSEVENT_KEY_RELEASE:
 		switch(e->code) {
 		case KEY_Z:
-			cur = sdl_getTicks();
+			cur = sys_get_ticks();
 			if (500 < (cur - sact.zofftime) || !sact.zdooff) {
 				slist_foreach(sact.sp_zhide, cb_focused_zkey, &update);
 				sact.zhiding = false;
diff --git a/modules/SACT/sprite_keywait.c b/modules/SACT/sprite_keywait.c
index f008416..ff44e64 100644
--- a/modules/SACT/sprite_keywait.c
+++ b/modules/SACT/sprite_keywait.c
@@ -29,7 +29,6 @@
 #include "portab.h"
 #include "system.h"
 #include "list.h"
-#include "sdl_core.h"
 #include "ags.h"
 #include "nact.h"
 #include "input.h"
@@ -67,7 +66,7 @@ static void hidesprite(sprite_t *sp) {
    スプライトがドロップされた時の各種処理を含む
 */
 static bool waitcond(int endtime) {
-	int curtime = sdl_getTicks();
+	int curtime = sys_get_ticks();
 	if (curtime >= endtime) return true;
 	
 	if (sact.dropped) {
@@ -144,7 +143,7 @@ void sp_keywait(int *vOK, int *vRND, int *vD01, int *vD02, int *vD03, int timeou
 	}
 	
 	// 終了時間の計算
-	curtime = sdl_getTicks();
+	curtime = sys_get_ticks();
 	endtime = timeout < 0 ? INT_MAX : (curtime + timeout * 10);
 	
 	// スプライトキー待ちメイン
diff --git a/modules/SACT/sprite_move.c b/modules/SACT/sprite_move.c
index 03360e0..e5c9d10 100644
--- a/modules/SACT/sprite_move.c
+++ b/modules/SACT/sprite_move.c
@@ -32,7 +32,6 @@
 #include "nact.h"
 #include "sact.h"
 #include "sprite.h"
-#include "sdl_core.h"
 
 /*
 
@@ -161,14 +160,14 @@ void spev_move_waitend(sprite_t *sp, int dx, int dy, int time) {
 	sp->move.time = 0;
 	
 	sact.movelist = slist_append(sact.movelist, sp);
-	sact.movestarttime = sdl_getTicks();
+	sact.movestarttime = sys_get_ticks();
 	slist_foreach(sact.movelist, spev_move_setup, NULL);
 	slist_free(sact.movelist);
 	sact.movelist = NULL;
 	
 	while (sp->move.moving) {
 		nact->callback();
-		sdl_wait_vsync();
+		sys_wait_vsync();
 	}
 }
 
@@ -187,7 +186,7 @@ void spev_wait4moving_sp() {
 		
 		while (sp->move.moving) {
 			nact->callback();
-			sdl_wait_vsync();
+			sys_wait_vsync();
 		}
 	}
 }
diff --git a/modules/SACT/sprite_msg.c b/modules/SACT/sprite_msg.c
index 6973d5e..6dd89ed 100644
--- a/modules/SACT/sprite_msg.c
+++ b/modules/SACT/sprite_msg.c
@@ -29,7 +29,6 @@
 
 #include "portab.h"
 #include "system.h"
-#include "sdl_core.h"
 #include "ags.h"
 #include "nact.h"
 #include "input.h"
@@ -268,7 +267,7 @@ void smsg_out(int wNum, int wSize, int wColorR, int wColorG, int wColorB, int wF
 		char mbuf[20], rbuf[20];
 		int cw, delta, wcnt;
 		
-		wcnt = sdl_getTicks();
+		wcnt = sys_get_ticks();
 		
 		mbuf[0] = rbuf[0] = '\0';
 		msg = get_char(msg, mbuf, rbuf, sizeof(mbuf) -1); 
@@ -316,7 +315,7 @@ void smsg_out(int wNum, int wSize, int wColorR, int wColorG, int wColorB, int wF
 			needupdate = false;
 			
 			// keywait
-			delta = sdl_getTicks() - wcnt;
+			delta = sys_get_ticks() - wcnt;
 			if (delta < wSpeed) {
 				if (sys_keywait(wSpeed - delta, KEYWAIT_NONCANCELABLE)) {
 					
@@ -420,7 +419,7 @@ int smsg_keywait(int wNum1, int wNum2, int msglen) {
 	sact.waitkey = -1;
 	
 	while (sact.waitkey == -1 && !nact->is_quit) {
-		int st = sdl_getTicks();
+		int st = sys_get_ticks();
 		int interval = 25;
 		
 		// アニメパターンがある場合、その更新
@@ -434,7 +433,7 @@ int smsg_keywait(int wNum1, int wNum2, int msglen) {
 			update_mark(minfo[j].sp, minfo[j].cg);
 			i++;
 		} 
-		sys_keywait(interval - (sdl_getTicks() - st), KEYWAIT_NONCANCELABLE);
+		sys_keywait(interval - (sys_get_ticks() - st), KEYWAIT_NONCANCELABLE);
 	}
 	
 	sact.waittype = KEYWAIT_NONE;
diff --git a/modules/SACT/sprite_quake.c b/modules/SACT/sprite_quake.c
index e304b4b..3aa86a9 100644
--- a/modules/SACT/sprite_quake.c
+++ b/modules/SACT/sprite_quake.c
@@ -31,7 +31,6 @@
 #include "input.h"
 #include "sact.h"
 #include "sprite.h"
-#include "sdl_core.h"
 #include "randMT.h"
 
 /*
@@ -49,9 +48,9 @@ void sp_quake_sprite(int wType, int wAmplitudeX, int wAmplitudeY, int wCount, in
 	int i = 0, key;
 	SList *node;
 	
-	edtime = wCount * 10 + sdl_getTicks();
+	edtime = wCount * 10 + sys_get_ticks();
 	
-	while ((curtime = sdl_getTicks()) < edtime) {
+	while ((curtime = sys_get_ticks()) < edtime) {
 		if (wType == 0) { // 全てのスプライトを同じように動かす
 			int adjx = (int)(genrand() * wAmplitudeX/2);
 			int adjy = (int)(genrand() * wAmplitudeY/2);
diff --git a/modules/SACT/sprite_tevent.c b/modules/SACT/sprite_tevent.c
index a803567..5b3b196 100644
--- a/modules/SACT/sprite_tevent.c
+++ b/modules/SACT/sprite_tevent.c
@@ -33,7 +33,6 @@
 #include "nact.h"
 #include "sact.h"
 #include "sprite.h"
-#include "sdl_core.h"
 
 /*
 
@@ -63,7 +62,7 @@ static void tevent_callback(agsevent_t *e) {
 	int update = 0;
 	
 	// SP_MOVE の同期移動のためのカウンタの読み込み
-	sact.movecurtime = sdl_getTicks();
+	sact.movecurtime = sys_get_ticks();
 	
 	for (node = sact.teventlisteners; node; node = node->next) {
 		sprite_t *sp = (sprite_t *)node->data;
diff --git a/modules/SACT/sprite_update.c b/modules/SACT/sprite_update.c
index 96161b3..eef2e5b 100644
--- a/modules/SACT/sprite_update.c
+++ b/modules/SACT/sprite_update.c
@@ -28,7 +28,6 @@
 
 #include "portab.h"
 #include "system.h"
-#include "sdl_core.h"
 #include "ags.h"
 #include "sact.h"
 #include "sprite.h"
@@ -92,7 +91,7 @@ void sp_update_all(bool syncscreen) {
 	// スプライト移動がある場合は移動開始
 	if (sact.movelist) {
 		// 移動開始時間を合わせる
-		sact.movestarttime = sdl_getTicks();
+		sact.movestarttime = sys_get_ticks();
 		slist_foreach(sact.movelist, spev_move_setup, NULL);
 		slist_free(sact.movelist);
 		sact.movelist = NULL;
diff --git a/modules/ShGraph/ShGraph.c b/modules/ShGraph/ShGraph.c
index 90a6ca9..0a2ef5a 100644
--- a/modules/ShGraph/ShGraph.c
+++ b/modules/ShGraph/ShGraph.c
@@ -36,7 +36,6 @@
 #include "nact.h"
 #include "ags.h"
 #include "music.h"
-#include "sdl_core.h"
 #include "hacks.h"
 
 #define SLOT 40
@@ -451,7 +450,7 @@ static void PlayAnimeData() {
 	dib = ags_getDIB();
 	
 	for (loop = 0; loop < p1; loop++) {
-		int cnt = sdl_getTicks();
+		int cnt = sys_get_ticks();
 		is_backcopied = false;
 		
 		for (i = 0; i < SLOT; i++) {
@@ -528,9 +527,9 @@ static void PlayAnimeData() {
 		if (is_backcopied && !SDL_RectEmpty(&maprect))
 			ags_updateArea(maprect.x, maprect.y, maprect.w, maprect.h);
 
-		int now = sdl_getTicks();
+		int now = sys_get_ticks();
 		if (now - cnt < interval) {
-			sdl_sleep(interval - (now-cnt));
+			sys_sleep(interval - (now-cnt));
 		}
 	}
 }
diff --git a/modules/ShPort/ShPort.c b/modules/ShPort/ShPort.c
index 12c2902..6169ab2 100644
--- a/modules/ShPort/ShPort.c
+++ b/modules/ShPort/ShPort.c
@@ -35,7 +35,6 @@
 #include "system.h"
 #include "xsystem35.h"
 #include "modules.h"
-#include "sdl_core.h"
 #include "input.h"
 #include "menu.h"
 
@@ -54,7 +53,7 @@ static void OutputMessageBox(void) { /* 0 */
 	char *title_utf8 = toUTF8(svar_get(title));
 	char *msg_utf8 = toUTF8(svar_get(msg));
 
-	sdl_showMessageBox(MESSAGEBOX_INFO, title_utf8, msg_utf8);
+	sys_show_message_box(MESSAGEBOX_INFO, title_utf8, msg_utf8);
 
 	free(title_utf8);
 	free(msg_utf8);
diff --git a/modules/tDemo/tDemo.c b/modules/tDemo/tDemo.c
index c0024d9..3863699 100644
--- a/modules/tDemo/tDemo.c
+++ b/modules/tDemo/tDemo.c
@@ -31,7 +31,6 @@
 #include "input.h"
 #include "bgm.h"
 #include "gfx.h"
-#include "sdl_core.h"
 #include "cg.h"
 #include "jpeg.h"
 
@@ -73,9 +72,9 @@ static void Run() {
 
 	musbgm_play(TDEMO_MUSIC_NO, 0, 100, 0);
 
-	uint32_t start = sdl_getTicks();
+	uint32_t start = sys_get_ticks();
 	while (!nact->is_quit) {
-		int i = (sdl_getTicks() - start) / (1000 / FPS);
+		int i = (sys_get_ticks() - start) / (1000 / FPS);
 		if (i >= alk->datanum)
 			break;
 
@@ -90,7 +89,7 @@ static void Run() {
 			WARNING("Cannot decode CG %d", i);
 		}
 
-		int wait_ms = (i + 1) * (1000 / FPS) - (sdl_getTicks() - start);
+		int wait_ms = (i + 1) * (1000 / FPS) - (sys_get_ticks() - start);
 		if (wait_ms > 0) {
 			if (sys_keywait(wait_ms, KEYWAIT_CANCELABLE))
 				break;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 06cdc1c..a21377b 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -89,6 +89,7 @@ target_sources(xsystem35 PRIVATE
   sdl_cursor.c
   sdl_event.c
   selection.c
+  system.c
   texthook.c
   variable.c
   vsp.c
diff --git a/src/ags.c b/src/ags.c
index b02e78a..5f007e9 100644
--- a/src/ags.c
+++ b/src/ags.c
@@ -599,10 +599,10 @@ void ags_alpha_setPixel(int x, int y, int w, int h, uint8_t *b) {
 
 void ags_runEffect(int duration_ms, bool cancelable, ags_EffectStepFunc step, void *arg) {
 	unsigned wflags = cancelable ? KEYWAIT_CANCELABLE : KEYWAIT_NONCANCELABLE;
-	int start = sdl_getTicks();
-	for (int t = 0; t < duration_ms; t = sdl_getTicks() - start) {
+	int start = sys_get_ticks();
+	for (int t = 0; t < duration_ms; t = sys_get_ticks() - start) {
 		step(arg, (float)t / duration_ms);
-		int key = sys_keywait(start + t + 16 - sdl_getTicks(), wflags);
+		int key = sys_keywait(start + t + 16 - sys_get_ticks(), wflags);
 		if (cancelable && key) {
 			nact->waitcancel_key = key;
 			break;
@@ -724,7 +724,7 @@ void ags_setCursorLocation(int x, int y, bool is_dibgeo, bool for_selection) {
 		// navigation.
 		sdl_setCursorInternalLocation(x, y);
 		EM_ASM({ xsystem35.shell.showMouseMoveEffect($0, $1); }, x, y);
-		sdl_sleep(cursor_move_time);
+		sys_sleep(cursor_move_time);
 	}
 #else
 	if (nact->ags.mouse_warp_enabled) {
@@ -736,12 +736,12 @@ void ags_setCursorLocation(int x, int y, bool is_dibgeo, bool for_selection) {
 			int xi = ((dx*i*i*i) >> 9) - ((3*dx*i*i)>> 6) + ((3*dx*i) >> 3) + p.x;
 			int yi = ((dy*i*i*i) >> 9) - ((3*dy*i*i)>> 6) + ((3*dy*i) >> 3) + p.y;
 			sdl_setCursorLocation(xi, yi);
-			sdl_sleep(cursor_move_time / 7);
+			sys_sleep(cursor_move_time / 7);
 		}
 		sdl_setCursorLocation(x, y);
 	} else if (!for_selection) {
 		sdl_setCursorInternalLocation(x, y);
-		sdl_sleep(cursor_move_time);
+		sys_sleep(cursor_move_time);
 	}
 #endif
 }
diff --git a/src/bgm.emscripten.c b/src/bgm.emscripten.c
index c835062..486868f 100644
--- a/src/bgm.emscripten.c
+++ b/src/bgm.emscripten.c
@@ -24,7 +24,7 @@
 #include "nact.h"
 #include "bgm.h"
 #include "bgi.h"
-#include "sdl_core.h"
+#include "system.h"
 
 bool musbgm_init(DRIFILETYPE type, int base_no) {
 	if (type == DRIFILE_BGM)
@@ -84,6 +84,6 @@ void musbgm_wait(int no, int timeout) {
 	for (int i = 0; i * 16 < timeout * 10; i++) {
 		if (!musbgm_isplaying(no))
 			break;
-		sdl_wait_vsync();
+		sys_wait_vsync();
 	}
 }
diff --git a/src/cdrom.emscripten.c b/src/cdrom.emscripten.c
index 435e7fb..bdaba61 100644
--- a/src/cdrom.emscripten.c
+++ b/src/cdrom.emscripten.c
@@ -24,6 +24,7 @@
 #include "portab.h"
 #include "cdrom.h"
 #include "scheduler.h"
+#include "system.h"
 
 static bool cdrom_init(char *playlist) {
 	return true;
diff --git a/src/cmd2F.c b/src/cmd2F.c
index 2fd7384..0825da7 100644
--- a/src/cmd2F.c
+++ b/src/cmd2F.c
@@ -39,7 +39,6 @@
 #include "hankaku.h"
 #include "ags.h"
 #include "gfx.h"
-#include "sdl_core.h"
 #include "ald_manager.h"
 #include "LittleEndian.h"
 #include "hacks.h"
@@ -944,7 +943,7 @@ void commands2F5A() {
 	char *t1;
 	
 	t1 = toUTF8(sText);
-	sdl_showMessageBox(MESSAGEBOX_INFO, nact->game_title_utf8, t1);
+	sys_show_message_box(MESSAGEBOX_INFO, nact->game_title_utf8, t1);
 	free(t1);
 	
 	TRACE("strMessageBox %s:", sText);
@@ -955,7 +954,7 @@ void commands2F5B() {
 	char *t1;
 	
 	t1 = toUTF8(svar_get(eNum));
-	sdl_showMessageBox(MESSAGEBOX_INFO, nact->game_title_utf8, t1);
+	sys_show_message_box(MESSAGEBOX_INFO, nact->game_title_utf8, t1);
 	free(t1);
 	
 	TRACE("strMessageBoxStr %d:", eNum);
diff --git a/src/cmdv.c b/src/cmdv.c
index ffe235e..4805027 100644
--- a/src/cmdv.c
+++ b/src/cmdv.c
@@ -27,7 +27,6 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include "portab.h"
-#include "sdl_core.h"
 #include "scheduler.h"
 #include "xsystem35.h"
 #include "scenario.h"
@@ -760,7 +759,7 @@ void commandVA() { /* from Panyo */
 			/* 開始 (p3=コマ数,0:無限(開始位置==終了位置のとき))*/
 			inAnimation = true;
 			VAcmd[p1].elaspCut  = 0;
-			VAcmd[p1].startTime = sdl_getTicks();
+			VAcmd[p1].startTime = sys_get_ticks();
 			VAcmd[p1].totalCut  = p3;
 			
 			if (p3 == 0) {
@@ -784,7 +783,7 @@ void commandVA() { /* from Panyo */
 				/* キー抜け無し ,p3=0は指定不可 */
 				while(VAcmd[p1].state == VA_RUNNING) {
 					va_animationAlone(p1);
-					sdl_sleep(10);
+					sys_sleep(10);
 				}
 				va_drawUnit(p1);
 				va_updateUnit(p1);
@@ -794,7 +793,7 @@ void commandVA() { /* from Panyo */
 				VAcmd[p1].rewrite = true;
 				while(VAcmd[p1].state == VA_RUNNING) {
 					va_animationAlone(p1);
-					sdl_sleep(10);
+					sys_sleep(10);
 					key = sys_getInputInfo();
 					if (key != 0) {
 						sysVar[0] = key;
@@ -1003,7 +1002,7 @@ static void va_animationAlone(int i) {
 static void va_update() {
 	bool proceeding = false;
 	int i;
-	int curTime = sdl_getTicks();
+	int curTime = sys_get_ticks();
 	
 	for (i = 0; i < VACMD_MAX; i++) {
 		if (VAcmd[i].state == VA_RUNNING) {
diff --git a/src/cmdy.c b/src/cmdy.c
index 7817a20..2b23ea5 100644
--- a/src/cmdy.c
+++ b/src/cmdy.c
@@ -31,7 +31,6 @@
 #include "input.h"
 #include "scenario.h"
 #include "cmd_check.h"
-#include "sdl_core.h"
 #include "scheduler.h"
 #include "music_cdrom.h"
 #include "hacks.h"
@@ -75,7 +74,7 @@ static void rance4_Y3_IM_hack() {
 
 	int button_pressed = sys_getInputInfo();
 	if (!button_pressed) {
-		sdl_wait_vsync();
+		sys_wait_vsync();
 		count = 0;
 	}
 	commandIM();
diff --git a/src/cmdz.c b/src/cmdz.c
index 9d225a6..67c66bd 100644
--- a/src/cmdz.c
+++ b/src/cmdz.c
@@ -28,7 +28,6 @@
 #include "portab.h"
 #include "xsystem35.h"
 #include "gfx.h"
-#include "sdl_core.h"
 #include "scheduler.h"
 #include "ags.h"
 #include "scenario.h"
@@ -45,13 +44,13 @@ static struct {
 } counters[257];  // [0] for ZT 1-5, [1..256] for ZT 10-11
 
 static void reset_counter(int num, int divisor, int offset) {
-	counters[num].base = sdl_getTicks() - offset;
+	counters[num].base = sys_get_ticks() - offset;
 	counters[num].divisor = divisor;
 }
 
 static uint32_t get_counter(int num) {
 	scheduler_on_event(SCHEDULER_EVENT_TIMER_CHECK);
-	return sdl_getTicks() - counters[num].base;
+	return sys_get_ticks() - counters[num].base;
 }
 
 void commandZC() {
diff --git a/src/dri.c b/src/dri.c
index 1cb668a..3114046 100644
--- a/src/dri.c
+++ b/src/dri.c
@@ -29,7 +29,6 @@
 #include "system.h"
 #include "LittleEndian.h"
 #include "dri.h"
-#include "sdl_core.h"
 
 static bool read_index(int volume, drifiles *d, FILE *fp) {
 	fseek(fp, 0L, SEEK_END);
@@ -142,7 +141,7 @@ static void warn_missing_ald(drifiles *d, int no) {
 	} else {
 		snprintf(msgbuf, sizeof(msgbuf), "Cannot read resource #%d.", no);
 	}
-	sdl_showMessageBox(MESSAGEBOX_WARNING, "xsystem35", msgbuf);
+	sys_show_message_box(MESSAGEBOX_WARNING, "xsystem35", msgbuf);
 }
 
 dridata *dri_getdata(drifiles *d, int no) {
diff --git a/src/ecopy.c b/src/ecopy.c
index 44aa42b..48041c8 100644
--- a/src/ecopy.c
+++ b/src/ecopy.c
@@ -28,7 +28,6 @@
 
 #include "portab.h"
 #include "gfx.h"
-#include "sdl_core.h"
 #include "input.h"
 #include "ags.h"
 #include "system.h"
@@ -40,7 +39,7 @@ static bool ecp_cancel;
 #define EC_WAIT \
 	if ((key |= sys_getInputInfo()) && ecp_cancel) break; \
 	do {												  \
-		int wait_ms = cnt - sdl_getTicks();				  \
+		int wait_ms = cnt - sys_get_ticks();				  \
 		if (wait_ms >= 16)								  \
 			key = sys_keywait(wait_ms, ecp_cancel ? KEYWAIT_CANCELABLE : KEYWAIT_NONCANCELABLE); \
 	} while (0)
@@ -61,7 +60,7 @@ static int eCopyArea5(int sx, int sy, int w, int h, int dx, int dy, int opt) {
 	static int hx[16]={ 0,32,16,48, 0,32,16,48,16,48, 0,32,16,48, 0,32};
 	static int hy[16]={ 0, 0,16,16,32,32,48,48, 0, 0,16,16,32,32,48,48};
 	
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 16; i++) {
 		cnt += waitcnt;
 		for (y = 0; y < (h -63); y += 64) {
@@ -82,7 +81,7 @@ static int eCopyArea6(int dx, int dy, int w, int h, int opt) {
 	int i, x, y, key = 0, cnt;
 	int waitcnt = opt == 0 ? 30 : opt;
 
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 7; i++) {
 		cnt += waitcnt;
 		for (x = 0; x < (w -63); x += 64) {
@@ -106,7 +105,7 @@ static int eCopyArea9(int sx, int sy, int w, int h, int dx, int dy, int opt) {
 	static int hintY[4] = {0,8,8,0};
 
 	
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 4; i++) {
 		cnt+=waitcnt;
 		for (y = 0; y < h -15; y+=16) {
@@ -126,7 +125,7 @@ static int eCopyArea16(int dx, int dy, int w, int h, int opt) {
 	int i, x, key = 0, cnt;
 	int waitcnt = opt == 0 ? 30 : opt;
 	
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 8; i++) {
 		cnt += waitcnt;
 		for (x = 0; x < (w -15); x += 16) {
@@ -144,7 +143,7 @@ static int eCopyArea17(int dx, int dy, int w, int h, int opt) {
 	int waitcnt = opt == 0 ? 30 : opt;
 
 #define E17X 18
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < E17X; i++) {
 		cnt += waitcnt;
 		for (y = 0; y < (h - E17X + 1); y += E17X) {
@@ -160,7 +159,7 @@ static int eCopyArea22(int sx, int sy, int w, int h, int dx, int dy, int opt) {
 	int i, x, y, key = 0, cnt;
 	int waitcnt = opt == 0 ? 80 : opt;
 	
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 2; i++) {
 		cnt += waitcnt;
 		for (y = 0; y < (h -3); y+=4) {
@@ -185,7 +184,7 @@ static int eCopyArea23(int sx, int sy, int w, int h, int dx, int dy, int opt) {
 	static int hintX[4] = {0,2,2,0};
 	static int hintY[4] = {0,2,0,2};
 	
-	cnt = sdl_getTicks();
+	cnt = sys_get_ticks();
 	for (i = 0; i < 4; i++) {
 		cnt += waitcnt;
 		for (y = 0; y < (h -3); y+=4) {
diff --git a/src/gfx_draw.c b/src/gfx_draw.c
index 45b0428..243c0af 100644
--- a/src/gfx_draw.c
+++ b/src/gfx_draw.c
@@ -36,8 +36,6 @@
 #include "system.h"
 #include "gfx.h"
 #include "gfx_private.h"
-#include "sdl_core.h"
-#include "scheduler.h"
 #include "font.h"
 #include "ags.h"
 #include "image.h"
@@ -66,43 +64,6 @@ void gfx_updateScreen(void) {
 	gfx_dirty = false;
 }
 
-uint32_t sdl_getTicks(void) {
-	return SDL_GetTicks();
-}
-
-void sdl_sleep(int msec) {
-	gfx_updateScreen();
-	dbg_onsleep();
-#ifdef __EMSCRIPTEN__
-	emscripten_sleep(msec);
-#else
-	SDL_Delay(msec);
-#endif
-	scheduler_on_event(SCHEDULER_EVENT_SLEEP);
-}
-
-#ifdef __EMSCRIPTEN__
-EM_JS(void, wait_vsync, (void), {
-	// We need a `return` here for JSPI support (ASYNCIFY=2).
-	return Asyncify.handleSleep(function(wakeUp) {
-		window.requestAnimationFrame(function() {
-			wakeUp();
-		});
-	});
-});
-#endif
-
-void sdl_wait_vsync() {
-	gfx_updateScreen();
-	dbg_onsleep();
-#ifdef __EMSCRIPTEN__
-	wait_vsync();
-#else
-	SDL_Delay(16);
-#endif
-	scheduler_on_event(SCHEDULER_EVENT_SLEEP);
-}
-
 /* off-screen の指定領域を Main Window へ転送 */
 void gfx_updateArea(SDL_Rect *rect, SDL_Point *dst) {
 	SDL_Rect sw = {0, 0, main_surface->w, main_surface->h};
diff --git a/src/gfx_video.c b/src/gfx_video.c
index b5a8263..9c0b026 100644
--- a/src/gfx_video.c
+++ b/src/gfx_video.c
@@ -247,16 +247,6 @@ void gfx_setWindowSize(int w, int h) {
 #endif
 }
 
-void sdl_showMessageBox(enum messagebox_type type, const char* title_utf8, const char* message_utf8) {
-	uint32_t flags = 0;
-	switch (type) {
-	case MESSAGEBOX_ERROR: flags = SDL_MESSAGEBOX_ERROR; break;
-	case MESSAGEBOX_WARNING: flags = SDL_MESSAGEBOX_WARNING; break;
-	case MESSAGEBOX_INFO: flags = SDL_MESSAGEBOX_INFORMATION; break;
-	}
-	SDL_ShowSimpleMessageBox(flags, title_utf8, message_utf8, gfx_window);
-}
-
 void gfx_setIntegerScaling(bool enable) {
 	SDL_RenderSetIntegerScale(gfx_renderer, enable);
 }
diff --git a/src/input.c b/src/input.c
index e50bad6..801878b 100644
--- a/src/input.c
+++ b/src/input.c
@@ -100,14 +100,14 @@ int sys_keywait(int msec, unsigned flags) {
 	}
 
 	int key=0, n;
-	int end = msec == INT_MAX ? INT_MAX : sdl_getTicks() + msec;
+	int end = msec == INT_MAX ? INT_MAX : sys_get_ticks() + msec;
 	while (!nact->is_quit &&
 		   !((flags & KEYWAIT_SKIPPABLE) && msgskip_isSkipping()) &&
-		   (n = end - sdl_getTicks()) > 0) {
+		   (n = end - sys_get_ticks()) > 0) {
 		if (n <= 16)
-			sdl_sleep(n);
+			sys_sleep(n);
 		else
-			sdl_wait_vsync();
+			sys_wait_vsync();
 		nact->callback();
 		key = sys_getInputInfo();
 		cancel_yield();  // We just yielded!
@@ -122,7 +122,7 @@ void sys_hit_any_key() {
 	if (msgskip_isSkipping()) {
 		if (msgskip_getFlags() & MSGSKIP_STOP_ON_CLICK && sys_getInputInfo())
 			msgskip_activate(false);
-		sdl_sleep(30);
+		sys_sleep(30);
 		return;
 	}
 
diff --git a/src/message.c b/src/message.c
index b8dac1d..f4334d7 100644
--- a/src/message.c
+++ b/src/message.c
@@ -29,7 +29,6 @@
 
 #include "portab.h"
 #include "windowframe.h"
-#include "sdl_core.h"
 #include "xsystem35.h"
 #include "message.h"
 #include "variable.h"
@@ -140,7 +139,7 @@ void msg_putMessage(const char *m) {
 				ags_updateArea(drawn.x, drawn.y, drawn.w, drawn.h);
 				break;
 			}
-			sdl_sleep(nact->messagewait_time * 10);
+			sys_sleep(nact->messagewait_time * 10);
 			nact->callback();
 		}
 	} else {
diff --git a/src/pcm.sdlmixer.c b/src/pcm.sdlmixer.c
index 4aaf4ae..70a115a 100644
--- a/src/pcm.sdlmixer.c
+++ b/src/pcm.sdlmixer.c
@@ -34,7 +34,6 @@
 #include "dri.h"
 #include "music_pcm.h"
 #include "music_private.h"
-#include "sdl_core.h"
 #include "nact.h"
 #include "LittleEndian.h"
 #include "mmap.h"
@@ -237,7 +236,7 @@ bool muspcm_start(int slot, int loop) {
 	if (Mix_PlayChannel(slot, slots[slot].chunk, loop - 1) < 0)
 		return false;
 
-	slots[slot].start_time = sdl_getTicks();
+	slots[slot].start_time = sys_get_ticks();
 	return true;
 }
 
@@ -277,7 +276,7 @@ int muspcm_getpos(int slot) {
 	if (!Mix_Playing(slot))
 		return 0;
 
-	int pos = sdl_getTicks() - slots[slot].start_time;
+	int pos = sys_get_ticks() - slots[slot].start_time;
 	if (pos == 0)
 		pos = 1;  // because 0 means "not playing"
 
diff --git a/src/scheduler.c b/src/scheduler.c
index 37992af..62fad03 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -18,7 +18,6 @@
 */
 #include "scheduler.h"
 #include "scenario.h"
-#include "sdl_core.h"
 #include "nact.h"
 #include "hacks.h"
 
@@ -87,13 +86,13 @@ void scheduler_on_event(enum scheduler_event event) {
 void scheduler_yield(void) {
 	switch (game_id) {
 	case GAME_AGAKE:
-		sdl_sleep(6);  // The slot game runs in a 6ms-cycle loop.
+		sys_sleep(6);  // The slot game runs in a 6ms-cycle loop.
 		break;
 	case GAME_PERSIOM:
-		sdl_sleep(10);  // The slot game runs in a 10ms-cycle loop.
+		sys_sleep(10);  // The slot game runs in a 10ms-cycle loop.
 		break;
 	default:
-		sdl_wait_vsync();
+		sys_wait_vsync();
 		break;
 	}
 }
diff --git a/src/sdl_core.h b/src/sdl_core.h
index 54e496b..09fd7d1 100644
--- a/src/sdl_core.h
+++ b/src/sdl_core.h
@@ -46,15 +46,6 @@ extern void sdl_setAutoRepeat(bool enable);
 extern SDL_Point sdl_translateMouseCoords(int x, int y);
 
 /* misc */
-enum messagebox_type {
-	MESSAGEBOX_ERROR,
-	MESSAGEBOX_WARNING,
-	MESSAGEBOX_INFO,
-};
-extern uint32_t sdl_getTicks(void);
-extern void sdl_sleep(int msec);
-extern void sdl_wait_vsync();
-extern void sdl_showMessageBox(enum messagebox_type type, const char* title_utf8, const char* message_utf8);
 extern bool sdl_inputString(struct inputstring_param *);
 extern void sdl_post_debugger_command(void *data);
 extern void sdl_handle_event(SDL_Event *e);
diff --git a/src/sdl_input.c b/src/sdl_input.c
index ac9f469..6098609 100644
--- a/src/sdl_input.c
+++ b/src/sdl_input.c
@@ -26,6 +26,7 @@
 #include "gfx_private.h"
 #include "menu.h"
 #include "nact.h"
+#include "system.h"
 
 #define XMARGIN 3
 #define YMARGIN 2
@@ -158,7 +159,7 @@ bool sdl_inputString(INPUTSTRING_PARAM *p) {
 	while (!input->done) {
 		sdl_getKeyInfo();  // message pump
 		nact->callback();
-		sdl_wait_vsync();
+		sys_wait_vsync();
 	}
 	SDL_StopTextInput();
 	sdl_custom_event_handler = NULL;
diff --git a/src/system.c b/src/system.c
new file mode 100644
index 0000000..1c447ce
--- /dev/null
+++ b/src/system.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2025 kichikuou <KichikuouChrome@gmail.com>
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+*/
+
+#include "system.h"
+#include <SDL.h>
+#include "debugger.h"
+#include "gfx.h"
+#include "gfx_private.h"
+#include "scheduler.h"
+#include "sdl_core.h"
+
+#ifdef __ANDROID__
+#include <android/log.h>
+#endif
+
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
+#ifdef DEBUG
+#define DEBUGLEVEL 2
+#else
+#define DEBUGLEVEL 0
+#endif /* DEBUG */
+
+static int debuglv = DEBUGLEVEL;
+
+void sys_set_debug_level(int level) {
+	debuglv = level;
+}
+
+void sys_message(int lv, char *format, ...) {
+	if (debuglv < lv)
+		return;
+
+	va_list args;
+	va_start(args, format);
+
+#ifdef __ANDROID__
+	const int prio_table[] = {
+		ANDROID_LOG_FATAL,
+		ANDROID_LOG_ERROR,
+		ANDROID_LOG_WARN,
+		ANDROID_LOG_INFO,
+		ANDROID_LOG_INFO,
+		ANDROID_LOG_VERBOSE,
+	};
+	int prio = prio_table[min(lv, 5)];
+	__android_log_vprint(prio, "xsystem35", format, args);
+#else
+	if (!dbg_console_vprintf(lv, format, args))
+		vfprintf(stderr, format, args);
+#endif
+	va_end(args);
+}
+
+void sys_error(char *format, ...) {
+	char buf[512];
+	va_list args;
+	
+	va_start(args, format);
+	vsnprintf(buf, sizeof buf, format, args);
+	va_end(args);
+	sys_show_message_box(MESSAGEBOX_ERROR, "xsystem35", buf);
+
+	sys35_remove();
+	exit(1);
+}
+
+void sys_exit(int code) {
+	sys35_remove();
+#ifdef __EMSCRIPTEN__
+	EM_ASM( xsystem35.shell.quit(); );
+	sys_sleep(1000000000);
+#else
+	exit(code);
+#endif
+}
+
+uint32_t sys_get_ticks(void) {
+	return SDL_GetTicks();
+}
+
+void sys_sleep(int msec) {
+	gfx_updateScreen();
+	dbg_onsleep();
+#ifdef __EMSCRIPTEN__
+	emscripten_sleep(msec);
+#else
+	SDL_Delay(msec);
+#endif
+	scheduler_on_event(SCHEDULER_EVENT_SLEEP);
+}
+
+#ifdef __EMSCRIPTEN__
+EM_JS(void, wait_vsync, (void), {
+	// We need a `return` here for JSPI support (ASYNCIFY=2).
+	return Asyncify.handleSleep(function(wakeUp) {
+		window.requestAnimationFrame(function() {
+			wakeUp();
+		});
+	});
+});
+#endif
+
+void sys_wait_vsync(void) {
+	gfx_updateScreen();
+	dbg_onsleep();
+#ifdef __EMSCRIPTEN__
+	wait_vsync();
+#else
+	SDL_Delay(16);
+#endif
+	scheduler_on_event(SCHEDULER_EVENT_SLEEP);
+}
+
+void sys_show_message_box(enum messagebox_type type, const char* title_utf8, const char* message_utf8) {
+	uint32_t flags = 0;
+	switch (type) {
+	case MESSAGEBOX_ERROR: flags = SDL_MESSAGEBOX_ERROR; break;
+	case MESSAGEBOX_WARNING: flags = SDL_MESSAGEBOX_WARNING; break;
+	case MESSAGEBOX_INFO: flags = SDL_MESSAGEBOX_INFORMATION; break;
+	}
+	SDL_ShowSimpleMessageBox(flags, title_utf8, message_utf8, gfx_window);
+}
diff --git a/src/system.h b/src/system.h
index b625453..3b7ad2e 100644
--- a/src/system.h
+++ b/src/system.h
@@ -24,12 +24,25 @@
 #ifndef __SYSTEM__
 #define __SYSTEM__
 
+#include <stdint.h>
 #include "config.h"
 
-/* should define in somewhere */ 
-extern void sys_error(char *format, ...);    /* show nessafe and exit system */
-extern void sys_exit(int code);              /* exit system with code */
-extern void sys_message(int lv, char *format, ...);  /* show various message */
+void sys_error(char *format, ...);    /* show message and exit system */
+void sys_exit(int code);              /* exit system with code */
+void sys_message(int lv, char *format, ...);  /* show various message */
+
+uint32_t sys_get_ticks(void);
+void sys_sleep(int msec);
+void sys_wait_vsync(void);
+
+enum messagebox_type {
+	MESSAGEBOX_ERROR,
+	MESSAGEBOX_WARNING,
+	MESSAGEBOX_INFO,
+};
+void sys_show_message_box(enum messagebox_type type, const char* title_utf8, const char* message_utf8);
+
+void sys35_remove(void);
 
 /*
  DEBUGLEVEL
@@ -38,12 +51,7 @@ extern void sys_message(int lv, char *format, ...);  /* show various message */
   1: warning only(output to terminal)
   2+: more message [devel relase default]
 */
-
-#ifdef DEBUG
-#define DEBUGLEVEL 2
-#else
-#define DEBUGLEVEL 0
-#endif /* DEBUG */
+void sys_set_debug_level(int level);
 
 #define NOMEMERR()        sys_error("Out of memory at %s()\n", __func__)
 
diff --git a/src/win/menubar.c b/src/win/menubar.c
index 9fa8b5e..749784e 100644
--- a/src/win/menubar.c
+++ b/src/win/menubar.c
@@ -57,7 +57,7 @@ static void saveScreenshot(void) {
 	if (!GetSaveFileName(&ofn))
 		return;
 	if (!save_screenshot(pathbuf)) {
-		sdl_showMessageBox(MESSAGEBOX_ERROR, "xsystem35", SDL_GetError());
+		sys_show_message_box(MESSAGEBOX_ERROR, "xsystem35", SDL_GetError());
 		SDL_ClearError();
 	}
 }
diff --git a/src/xsystem35.c b/src/xsystem35.c
index 4e895ad..a2a17b7 100644
--- a/src/xsystem35.c
+++ b/src/xsystem35.c
@@ -43,10 +43,6 @@
 #include <emscripten.h>
 #endif
 
-#ifdef __ANDROID__
-#include <android/log.h>
-#endif
-
 #ifdef _WIN32
 #include "win/dialog.h"
 #endif
@@ -78,14 +74,11 @@
 static char *gameResourceFile = "xsystem35.gr";
 static void    sys35_usage(bool verbose);
 static void    sys35_init();
-static void    sys35_remove();
 static void    sys35_ParseOption(int *argc, char **argv);
 static void    check_profile();
 
 static const char *render_driver = NULL;
 
-/* for debugging */
-static int debuglv = DEBUGLEVEL;
 enum {
 	DEBUGGER_DISABLED,
 	DEBUGGER_CUI,
@@ -156,54 +149,6 @@ static void sys35_usage(bool verbose) {
 	exit(1);
 }
 
-void sys_message(int lv, char *format, ...) {
-	if (debuglv < lv)
-		return;
-
-	va_list args;
-	va_start(args, format);
-
-#ifdef __ANDROID__
-	const int prio_table[] = {
-		ANDROID_LOG_FATAL,
-		ANDROID_LOG_ERROR,
-		ANDROID_LOG_WARN,
-		ANDROID_LOG_INFO,
-		ANDROID_LOG_INFO,
-		ANDROID_LOG_VERBOSE,
-	};
-	int prio = prio_table[min(lv, 5)];
-	__android_log_vprint(prio, "xsystem35", format, args);
-#else
-	if (!dbg_console_vprintf(lv, format, args))
-		vfprintf(stderr, format, args);
-#endif
-	va_end(args);
-}
-
-void sys_error(char *format, ...) {
-	char buf[512];
-	va_list args;
-	
-	va_start(args, format);
-	vsnprintf(buf, sizeof buf, format, args);
-	va_end(args);
-	sdl_showMessageBox(MESSAGEBOX_ERROR, "xsystem35", buf);
-
-	sys35_remove();
-	exit(1);
-}
-
-void sys_exit(int code) {
-	sys35_remove();
-#ifdef __EMSCRIPTEN__
-	EM_ASM( xsystem35.shell.quit(); );
-	sdl_sleep(1000000000);
-#else
-	exit(code);
-#endif
-}
-
 static void sys35_init() {
 	int i;
 	
@@ -229,7 +174,7 @@ static void sys35_init() {
 	msgskip_init(nact->files.msgskip);
 }
 
-static void sys35_remove() {
+void sys35_remove(void) {
 	dbg_quit();
 	mus_exit(); 
 	ags_remove();
@@ -337,7 +282,7 @@ static void sys35_ParseOption(int *argc, char **argv) {
 			nact->ags.noimagecursor = true;
 		} else if (0 == strcmp(argv[i], "-debuglv")) {
 			if (argv[i + 1] != NULL) {
-				debuglv = argv[i + 1][0] - '0';
+				sys_set_debug_level(argv[i + 1][0] - '0');
 			}
 		} else if (0 == strcmp(argv[i], "-version")) {
 			puts(VERSION);
@@ -523,7 +468,7 @@ int main(int argc, char **argv) {
 	
 	if (!initGameResource(&nact->files, gameResourceFile, savedir)) {
 #ifdef _WIN32
-		sdl_showMessageBox(MESSAGEBOX_ERROR, "xsystem35", "Cannot find scenario file (*SA.ALD)");
+		sys_show_message_box(MESSAGEBOX_ERROR, "xsystem35", "Cannot find scenario file (*SA.ALD)");
 		exit(1);
 #else
 		sys35_usage(true);