Make a Platform Game in Game Maker

This will require a little bit of experience with Game Maker. Don't do this for your first game.

Steps

Make a simple block sprite for your wall. Also make a sprite for your player. For the wall call it spr_wall and the player spr_player
Make an object called obj_wall and check the solid box.
Make sure you select the wall sprite.
Make an object and call it obj_player.
Make sure you select your player sprite.
For obj_player: go to add event and click Step then Step again. Then go to the control tab, and drag and drop the 'execute code' action.
Now in the code box put in
// simple Platforming code!//
if place_free(x,y+1)
{
gravity = 0.7
gravity_direction = 270
}
else
{
gravity=0
gravity_direction = 270
}
//the arrow keys<,>,^
if place_free(x-4,y)and keyboard_check(vk_left){x-=4}
if place_free(x+4,y)and keyboard_check(vk_right){x+=4}
if !place_free(x,y+1)
and keyboard_check(vk_up){vspeed=-10}
Just copy and paste.
For obj_player: Go to add event, then Collision, then with obj_wall.
Put in this code (go to the control tab and drag and drop 'execute code':

move_contact_solid(direction,12);
vspeed=0;
Make a room, call it room_1, make a level design by clicking with the selected object and save the room (click the tick at the top.)
Run the game!

GameMaker of course! This tutorial uses GM:S Professional, but Standard is also good. You'll also need a bit of experience in GML first before doing this tutorial.