That Flappy Bird game looked so simple I tried to see how fast I can recreate it. This took 4 or 5 days, playable but a lot left out, like sounds and fancy scene/collision management. Instead I just built it adhoc style all in MainWindow (only 5 methods needed) along with 3 very simple classes to hold geometries (XBPoint, XBRay, XBGap (the pipes)). Also my OpenGL framework and images pulled from the Happy Flappy Bird clone https://github.com/Hipo/happy-flappy-bird .
Maybe you build Flappy Bird too. It's the 101 of physics games: 1 input, a block, an array of blocks, floor, gravity, collision and drawing. How much and long can that take?
http://home.comcast.net/~trochoid/code/XoppyBird.zip press up to go, down to reset. ymmv