You know those days when you just don't know which game to play, or you think "Hey, it would be better if they added this or that in the game!" It happens to me a lot so I was told about a program where you can program your very own game. It is called Construct 2 and is pretty simple to use.
The first thing you must do is to go to the Construct 2 official webpage and hit the download button. You can pay to buy the premium account, but of course you can also use the free account. When you install it and activate it, you should be on the start page. Go to the top left corner and there will be a "New Empty Project" button. Click it and you get a layout for your game. In the next steps I will talk about how to make your game, but of course, you can try out the tutorials on the official website.
To make a platformer game you need images of a player and floors. For floors I used these Geometry Dash blocks, and for player I used another one. To make a player, you must double-click on the background, choose a Sprite, open an image from a file (in the top left corner), and click X. Your player will probably be too large so you can modify its size. On the left you should see a Behaviors button. Click it, click a plus, and add a Platform behavior (so you can play) and a Scroll To behavior (so the camera always follows the player.) Do the same thing for floors, but add just a Solid behavior. If you hold CTRL and click and drag an object, it will multiply. That way you can add floating platforms without going copy-paste all the time. Once you are done with the layout, you finished the easy part. Now comes the hard one.
If you go to the event sheet, you will see the Add Event button. Once you click it, you will see all the Sprites you made. You can now add events. For example: Add event-Player-Is On Layout Border. Then you add actions. For example: Player-Destroy. This means that if a player comes to a contact with the layout border, it will destroy. Hit the Run button. You will see your player goes where you tell him to go. If you want more, go to the official page or ask me in the comments. Bye!