reference code

#TouhouDanmakufu[Single]
#ScriptVersion[3]
#ID["Bound_and_Rebound"]
#Title["Disaster Sign 'Shock and Aftershock'"]
#Text["Resonating bullets are wonderful things, aren't they?"]
//#Image["./bar.png"]
//#Background["./tower.png"]
//#BGM["./boss.mp3"]
#Replay Name["Ear.Hard"]

let speed = 1;
let tick = 0;
let tick2 = 384;
let bossObj;
let bossX = 0;
let bossY = 0;
let imgBoss = GetCurrentScriptDirectory ~ "standin.png";

#include "script/default_system/Default_ShotConst.txt"

let difficulty = 2;
//0 = Easy
//1 = Normal
//2 = Hard
//3 = Lunatic
//4 = Ultra
//-1 = Stable
@Initialize {

	//boss defines
	bossObj = ObjEnemy_Create(OBJ_ENEMY_BOSS);
	ObjEnemy_Regist(bossObj);

	ObjMove_SetPosition(bossObj,192,-100);

	//move Seraph Midori to correct place
	ObjMove_SetDestAtSpeed(bossObj,192,120,5);

	mainTask;
}

@Event {
	//set boss timer
	alternative(GetEventType())
	case(EV_REQUEST_LIFE) {
		SetScriptResult(3000);
	}
	case(EV_REQUEST_TIMER) {
		SetScriptResult(60);
	}


}

@MainLoop {
	bossX = ObjMove_GetX(bossObj);
	bossY = ObjMove_GetY(bossObj);

	//collision
	ObjEnemy_SetIntersectionCircleToShot(bossObj,bossX,bossY,32);
	ObjEnemy_SetIntersectionCircleToPlayer(bossObj,bossX,bossY,16);
	yield;
}

@Finalize {

}

function angleToPlayer {
	let dir = atan2(GetPlayerY-bossY,GetPlayerX-bossX);
	return dir
}







//height == 448

task movement {
	let var_quake1 = CreateShotA1(bossX,bossY,3,0,DS_BALL_L_GREEN,0);
	let var_quake2 = CreateShotA1(bossX,bossY,3,180,DS_BALL_L_GREEN,0);
	let q1_x = ObjMove_GetX(var_quake1);
	let q1_y = ObjMove_GetY(var_quake1);
	let q2_x = ObjMove_GetX(var_quake2);
	let q2_y = ObjMove_GetY(var_quake2);
	function q1_angleToPlayer {
	let q1_atp = atan2(GetPlayerY-q1_y,GetPlayerX-q1_x);
	return q1_atp
}

function q2_angleToPlayer {
	let q2_atp = atan2(GetPlayerY-q2_y,GetPlayerX-q2_x);
	return q2_atp
}
		loop{

			let q1_atp = q1_angleToPlayer;
			let q2_atp = q2_angleToPlayer;
			if(q1_x > 384) { ObjMove_AddPatternA1(var_quake1,0,NO_CHANGE,q1_atp); }
			if(q1_x < 0) { ObjMove_AddPatternA1(var_quake1,0,NO_CHANGE,q1_atp); }
			if(q1_y > 448) { ObjMove_AddPatternA1(var_quake1,0,NO_CHANGE,q1_atp); }
			if(q1_y < 0) { ObjMove_AddPatternA1(var_quake1,0,NO_CHANGE,q1_atp); }
			if(q2_x > 384) { ObjMove_AddPatternA1(var_quake2,0,NO_CHANGE,q2_atp); }
			if(q2_x < 0) { ObjMove_AddPatternA1(var_quake2,0,NO_CHANGE,q2_atp); }
			if(q2_y > 448) { ObjMove_AddPatternA1(var_quake2,0,NO_CHANGE,q2_atp); }
			if(q2_y < 0) { ObjMove_AddPatternA1(var_quake2,0,NO_CHANGE,q2_atp); }
			yield;
		}
}
//Best function ever; very convenient
function wait(w) {
	loop(w) { yield; }
}

task mainTask {
	renderBoss;
	ObjMove_SetDestAtSpeed(bossObj,196,224,5);
	wait(70);
	movement;
}

task renderBoss {
	let dir;
	let speed;
	ObjPrim_SetTexture(bossObj,imgBoss);
	ObjSprite2D_SetSourceRect(bossObj,0,0,16,32);
	ObjSprite2D_SetDestCenter(bossObj);
	ObjRender_SetScaleXYZ(bossObj,2,2,0);

	while(!Obj_IsDeleted(bossObj)) {

	dir = ObjMove_GetAngle(bossObj);
	speed = ObjMove_GetSpeed(bossObj);
	if(speed == 0) { ObjSprite2D_SetSourceRect(bossObj,0,0,16,32);  ObjRender_SetAngleXYZ(bossObj,0,0,0); }
	else if(cos(dir) < 0) { ObjSprite2D_SetSourceRect(bossObj,0,0,16,32);  ObjRender_SetAngleXYZ(bossObj,0,0,0); }
	else if(cos(dir) > 0) { ObjSprite2D_SetSourceRect(bossObj,0,0,16,32);  ObjRender_SetAngleXYZ(bossObj,0,180,0); }

	yield;
	}
}