it seems that the gravity is reversed here. check collision mechanismus systema. player should be able to jump on platforms and stay on platforms normally as in Mario platformer game. each obstacle-platform should be as impenetrable wall in dependence of its current size. output only functions to add or fix, without full original code.: const canvas=document.getElementById("game-canvas");const context=canvas.getContext("2d");canvas.width=640;canvas.height=480;const GRAVITY=80;const ENEMY_RADIUS=10;const PLAYER_RADIUS=10;const TRACTION=.9;const OBSTACLE_COUNT=50;const OBSTACLE_GAP=0;let playerX=1e3;let playerY=100;let isPlayerAlive=true;let enemyX=1e3;let enemyY=100;let enemySpeedX=0;let enemySpeedY=0;let enemyMultiplier=0;let playerSpeedX=0;let playerSpeedY=0;let playerIsOnGround=false;let lasers=[];let shootingTimer=0;let obstacles=[];const obstacleWidth=100;const obstacleHeight=5;let offsetX=0;let offsetY=0;let scrollSpeed=1;function applyGravity(){if(!playerIsOnGround){playerSpeedY+=GRAVITY/60}}function applyTraction(){playerSpeedX*=TRACTION}function movePlayer(){if(!isPlayerAlive)return;playerX+=playerSpeedX;playerY+=playerSpeedY;if(playerX<0){playerX=0}if(playerX+PLAYER_RADIUS*2>canvas.width){playerX=canvas.width-PLAYER_RADIUS*2}context.fillStyle="pink";context.fillRect(playerX-offsetX,playerY-offsetY,PLAYER_RADIUS*2,PLAYER_RADIUS*2)}if(playerX<-PLAYER_RADIUS){playerX=canvas.width-PLAYER_RADIUS;generateNewObstacle()}if(playerX>canvas.width-PLAYER_RADIUS){playerX=-PLAYER_RADIUS;generateNewObstacle()}function moveEnemy(){if(!isPlayerAlive)return;const targetIndex=findNearestObstacle(playerX,playerY);const targetX=obstacles[targetIndex].x+obstacleWidth/2;const targetY=obstacles[targetIndex].y+obstacleHeight/2;const epsilon=.2;if(Math.abs(enemyX-targetX)>epsilon||Math.abs(enemyY-targetY)>epsilon){const angle=Math.atan2(targetY-enemyY,targetX-enemyX);enemySpeedX=Math.cos(angle)*2;enemySpeedY=Math.sin(angle)*2}else{enemySpeedX=0;enemySpeedY=0}enemyX+=enemySpeedX;enemyY+=enemySpeedY;context.fillStyle="cyan";context.fillRect(enemyX-ENEMY_RADIUS-offsetX,enemyY-ENEMY_RADIUS,ENEMY_RADIUS*2,ENEMY_RADIUS*2)}function findNearestObstacle(x,y){let minIndex=0;let minDistance=Number.MAX_VALUE;for(let i=0;i<obstacles.length;i++){const dx=x-(obstacles[i].x+obstacleWidth/2);const dy=y-(obstacles[i].y+obstacleHeight/2);const distance=Math.sqrt(dx*dx+dy*dy);if(distance<minDistance){minDistance=distance;minIndex=i}}return minIndex}function isColliding(x,y,width,height){let collisionDetected=false;let isPlayerOnTop=false;let nearestObstacle=null;let minDistance=Number.MAX_VALUE;for(const obstacle of obstacles){if(obstacle&&x<obstacle.x+obstacle.width&&x+width>obstacle.x&&y<obstacle.y+obstacle.height&&y+height>obstacle.y){const dx=Math.max(0,Math.min(x+width,obstacle.x+obstacle.width)-Math.max(x,obstacle.x));const dy=Math.max(0,Math.min(y+height,obstacle.y+obstacle.height)-Math.max(y,obstacle.y));const distance=Math.sqrt(dx*dx+dy*dy);if(distance<minDistance){minDistance=distance;nearestObstacle=obstacle}}}if(nearestObstacle){const dx=Math.max(0,Math.min(x+width,nearestObstacle.x+nearestObstacle.width)-Math.max(x,nearestObstacle.x));const dy=Math.max(0,Math.min(y+height,nearestObstacle.y+nearestObstacle.height)-Math.max(y,nearestObstacle.y));const distance=Math.sqrt(dx*dx+dy*dy);if(distance<PLAYER_RADIUS){if(dy>dx&&x+width/2>nearestObstacle.x&&x+width/2<nearestObstacle.x+nearestObstacle.width){playerY=nearestObstacle.y-PLAYER_RADIUS*2;playerSpeedY=0;playerIsOnGround=true;isPlayerOnTop=true}else if(dx>dy&&y+height/2>nearestObstacle.y&&y+height/2<nearestObstacle.y+nearestObstacle.height){if(playerX<nearestObstacle.x+nearestObstacle.width/2){playerX=nearestObstacle.x-PLAYER_RADIUS*2}else{playerX=nearestObstacle.x+nearestObstacle.width}playerSpeedX=0}collisionDetected=true}}if(!isPlayerOnTop){playerIsOnGround=false}return collisionDetected}function checkCollision(){if(isColliding(playerX,playerY,PLAYER_RADIUS*2,PLAYER_RADIUS*2)){playerY-=playerSpeedY;offsetY-=playerSpeedY;playerSpeedY=0;playerIsOnGround=true}else{playerIsOnGround=false}}function detectObstacleCollision(){for(const obstacle of obstacles){if(playerX+PLAYER_RADIUS*2>obstacle.x&&playerX<obstacle.x+obstacle.width&&playerY+PLAYER_RADIUS*2>obstacle.y&&playerY<obstacle.y+obstacle.height){if(playerX+PLAYER_RADIUS*2<obstacle.x+5){playerX=obstacle.x-PLAYER_RADIUS*2}else if(playerX>obstacle.x+obstacle.width-5){playerX=obstacle.x+obstacle.width}else{if(playerY+PLAYER_RADIUS*2<obstacle.y+5){playerY=obstacle.y-PLAYER_RADIUS*2;playerIsOnGround=true}if(playerY>obstacle.y+obstacle.height-5){playerY=obstacle.y+obstacle.height;playerSpeedY=0}}}if(enemyX+ENEMY_RADIUS*2>obstacle.x&&enemyX<obstacle.x+obstacle.width&&enemyY+ENEMY_RADIUS*2>obstacle.y&&enemyY<obstacle.y+obstacle.height){if(enemyX+ENEMY_RADIUS*2<obstacle.x+5){enemyX=obstacle.x-ENEMY_RADIUS*2}else if(enemyX>obstacle.x+obstacle.width-5){enemyX=obstacle.x+obstacle.width}else{if(enemyY+ENEMY_RADIUS*2<obstacle.y+5){enemyY=obstacle.y-ENEMY_RADIUS*2}else if(enemyY>obstacle.y+obstacle.height-5){enemyY=obstacle.y+obstacle.height;enemySpeedY=0}}}}}function shootLaser(){const laserSpeed=2;const angle=Math.atan2(playerX-enemyX);const laserSpeedX=Math.cos(angle)*laserSpeed;const laserSpeedY=Math.sin(angle)*laserSpeed;lasers.push({x:enemyX+ENEMY_RADIUS,y:enemyY+ENEMY_RADIUS,speedX:laserSpeedX,speedY:laserSpeedY})}function moveLasers(){let playerHit=false;for(let i=0;i<lasers.length;i++){const laser=lasers[i];laser.x+=laser.speedX;laser.y+=laser.speedY;if(!playerHit&&laser.x>=playerX&&laser.x<=playerX+PLAYER_RADIUS*2&&laser.y>=playerY&&laser.y<=playerY+PLAYER_RADIUS*2){const randomColor="rgb("+Math.floor(Math.random()*256)+","+Math.floor(Math.random()*256)+","+Math.floor(Math.random()*256)+")";context.strokeStyle=randomColor;context.beginPath();context.moveTo(laser.x,laser.y);context.lineTo(laser.x+laser.speedX,laser.y+laser.speedY);context.lineWidth=3;context.stroke();playerHit=true;isPlayerAlive=false}if(laser.x<0||laser.x>canvas.width||laser.y<0||laser.y>canvas.height){lasers.splice(i,1);i}}if(playerHit){playerX=-100;playerY=-100}}function drawLasers(){context.fillStyle="red";for(const laser of lasers){context.beginPath();context.arc(laser.x,laser.y,5,0,Math.PI*2);context.fill()}}function drawObstacles(){context.fillStyle="yellow";for(const obstacle of obstacles){context.fillRect(obstacle.x,obstacle.y,obstacle.width,obstacle.height)}if(obstacles.length&&obstacles[0].y>canvas.height){obstacles.shift();const obstacleX=Math.random()*(canvas.width-obstacleWidth);const obstacleY=obstacles[obstacles.length-1].y-canvas.height/OBSTACLE_COUNT-OBSTACLE_GAP;obstacles.push({x:obstacleX,y:obstacleY,width:obstacleWidth,height:obstacleHeight})}}function createObstacles(){for(let i=0;i<OBSTACLE_COUNT;i++){const obstacleX=Math.random()*(canvas.width-obstacleWidth);const obstacleY=i*(canvas.height/OBSTACLE_COUNT)+OBSTACLE_GAP;obstacles.push({x:obstacleX,y:obstacleY,width:obstacleWidth,height:obstacleHeight})}}function setPlayerStartPosition(){const startingObstacle=obstacles[0];playerX=startingObstacle.x+obstacleWidth/2-PLAYER_RADIUS;playerY=startingObstacle.y-PLAYER_RADIUS*2}function drawObstacles(){context.fillStyle="yellow";for(const obstacle of obstacles){context.fillRect(obstacle.x,obstacle.y,obstacle.width,obstacle.height)}}function generateNewObstacle(){obstacles.shift();const obstacleX=Math.random()*(canvas.width-obstacleWidth);const obstacleY=obstacles.length>0?obstacles[obstacles.length-1].y-canvas.height/OBSTACLE_COUNT-OBSTACLE_GAP:canvas.height;obstacles.push({x:obstacleX,y:obstacleY,width:obstacleWidth,height:obstacleHeight})}function checkEnemyDeath(){if(isPlayerAlive&&playerSpeedX>=0&&playerY+PLAYER_RADIUS*2>enemyY-ENEMY_RADIUS&&playerX+PLAYER_RADIUS*2>enemyX-ENEMY_RADIUS&&playerX<enemyX+ENEMY_RADIUS){playerIsOnGround=false;playerSpeedY=-20;setTimeout(()=>{playerSpeedY=0},100);enemyX=-100;setTimeout(spawnNewEnemy,1e3);enemyMultiplier++}}function spawnNewEnemy(){enemyX=Math.random()*(canvas.width-ENEMY_RADIUS*2);enemyY=Math.random()*(canvas.height-ENEMY_RADIUS*2);for(let i=0;i<enemyMultiplier-10;i++){shootLaser()}}function draw(timestamp){context.fillStyle="black";context.fillRect(0,0,canvas.width,canvas.height);const elapsedSeconds=(timestamp-lastFrameTime)/1e3;lastFrameTime=timestamp;applyGravity(elapsedSeconds);applyTraction();movePlayer();moveEnemy();moveLasers();detectObstacleCollision();drawLasers();drawObstacles();checkEnemyDeath();if(playerY<offsetY+PLAYER_RADIUS*2&&playerX>offsetX-PLAYER_RADIUS*2&&playerX<offsetX+obstacleWidth+PLAYER_RADIUS*2){offsetY-=canvas.height/OBSTACLE_COUNT;playerY+=canvas.height/OBSTACLE_COUNT;enemyY+=canvas.height/OBSTACLE_COUNT;generateNewObstacle()}requestAnimationFrame(draw)}let lastFrameTime=0;createObstacles();setPlayerStartPosition();draw();document.addEventListener("keydown",event=>{if(event.code==="KeyA"){playerSpeedX=-5}if(event.code==="KeyD"){playerSpeedX=5}if(event.code==="KeyW"&&playerIsOnGround){playerSpeedY=-20;playerIsOnGround=false}});document.addEventListener("keyup",event=>{if(event.code==="KeyA"||event.code==="KeyD"){playerSpeedX=0}});