RE, alors voila  la version Sans undertale :)

En gros, tu re-vas dans le dossier créé sur ton burau, et tu refais les étapes de ttalheure, sauf que tu copies ce code a la place de l'autre:

<canvas id="ctx" width="500" height="500" style="border:1px solid #000000;"></canvas>

<script>
var ctx = document.getElementById("ctx").getContext("2d");
ctx.font = '30px Arial';

var HEIGHT = 500;
var WIDTH = 500;
var timeWhenGameStarted = Date.now();   //return time in ms

var player = {
        x:50,
        spdX:30,
        y:40,
        spdY:5,
        name:'P',
        hp:10,
        width:20,
        height:20,
        color:'green',
};

var enemyList = {};


getDistanceBetweenEntity = function (entity1,entity2){  //return distance (number)
        var vx = entity1.x - entity2.x;
        var vy = entity1.y - entity2.y;
        return Math.sqrt(vx*vx+vy*vy);
}

testCollisionEntity = function (entity1,entity2){       //return if colliding (true/false)
        var rect1 = {
                x:entity1.x-entity1.width/2,
                y:entity1.y-entity1.height/2,
                width:entity1.width,
                height:entity1.height,
        }
        var rect2 = {
                x:entity2.x-entity2.width/2,
                y:entity2.y-entity2.height/2,
                width:entity2.width,
                height:entity2.height,
        }
        return testCollisionRectRect(rect1,rect2);

}

Enemy = function (id,x,y,spdX,spdY,width,height){
        var enemy3 = {
                x:x,
                spdX:spdX,
                y:y,
                spdY:spdY,
                name:'E',
                id:id,
                width:500,
                height:50,
                color:'red',
        };
        enemyList[id] = enemy3;

}

document.onmousemove = function(mouse){
        var mouseX = mouse.clientX;
        var mouseY = mouse.clientY;

        player.x = mouseX;
        player.y = mouseY;
}





updateEntity = function (something){
        updateEntityPosition(something);
        drawEntity(something);
}
updateEntityPosition = function(something){
        something.x += something.spdX;
        something.y += something.spdY;

        if(something.x < 0 || something.x > WIDTH){
                something.spdX = -something.spdX;
        }
        if(something.y < 0 || something.y > HEIGHT){
                something.spdY = -something.spdY;
        }
}

testCollisionRectRect = function(rect1,rect2){
        return rect1.x <= rect2.x+rect2.width
                && rect2.x <= rect1.x+rect1.width
                && rect1.y <= rect2.y + rect2.height
                && rect2.y <= rect1.y + rect1.height;
}


drawEntity = function(something){
        ctx.save();
        ctx.fillStyle = something.color;
        ctx.fillRect(something.x-something.width/2,something.y-something.height/2,something.width,something.height);
        ctx.restore();
}



update = function(){
        ctx.clearRect(0,0,WIDTH,HEIGHT);

        for(var key in enemyList){
                updateEntity(enemyList[key]);

                var isColliding = testCollisionEntity(player,enemyList[key]);
                if(isColliding){
                        player.hp = player.hp - 1;
                        if(player.hp <= 0){
                                var timeSurvived = Date.now() - timeWhenGameStarted;

                                console.log("You lost! You survived for " + timeSurvived + " ms.");
                                timeWhenGameStarted = Date.now();
                                player.hp = 10;
                        }
                }

        }

        drawEntity(player);
        ctx.fillText(player.hp + " Hp",0,30);
}

Enemy('E1',150,350,10,15,30,30);
Enemy('E2',250,350,10,-15,20,20);
Enemy('E3',250,150,10,-8,40,10);


setInterval(update,40);












</script>
VOILA