Brick Breaker

Each wall opens with a title card, and the ball waits on the paddle until you launch it — Space, a click on the field, or a tap. From then on the ball never stops: it bounces off the rails at the sides and top, off every brick it meets, and off the paddle, which is the one thing you control. Move it with the mouse, by dragging a finger along the field, or with the Left and Right arrow keys (A and D work too).

The bottom of the field is open. A ball that drops past the paddle is gone, and when the last ball in play goes you lose a life and the next one is served on the paddle. You start with three lives; an Extra life capsule adds one, up to 6. Break every brick that can break and the wall is cleared — metal bricks never break, and never have to. Clear the twelfth wall to win.

By where the ball lands on it, and nothing else. The centre of the paddle sends the ball straight up; the further out it lands, the wider it goes, evenly, to 60 degrees from straight up at either end. The direction the ball came in from plays no part, which is what makes aiming something you can learn: catch the ball in the same place and it leaves on the same line every time.

So a ball never leaves the paddle flatter than 30 degrees above horizontal, and no bounce anywhere on the field leaves it flatter than 20 degrees — without that floor, a ball that clips the corner of a brick can come away nearly level and spend half a minute ticking between the side rails.

A hit that cracks a strong or tough brick without breaking it is worth 10. An explosive brick destroys every brick in the eight cells around it outright, however many hits they had left, and a charge caught in the blast goes off in turn — so a line of them is a fuse. Every brick a blast takes counts towards your combo exactly as if the ball had broken it.

About one breakable brick in seven — 14% of each wall, never fewer than 4 capsules or more than 12 — hides a capsule, which drops when that brick breaks. Catch it on the paddle for its effect and 100 points. Which bricks carry which capsule is fixed by the game number when the wall is built, so replaying a game hides the same capsules in the same places. An Extra life appears at most once per wall.

Catching a capsule that is already running restarts its clock rather than stacking it, and different power-ups run together. Losing a life or clearing a wall ends every one of them. There are never more than 8 balls in play at once.

Every brick has a value — 50, 80, 100 or 150 — and the combo multiplies it. The first brick a ball breaks after leaving the paddle scores once, the second twice, the third three times, and so on up to ×8. Touch the paddle and the count starts again. Five bricks in a row off one bounce are worth 50 + 100 + 150 + 200 + 250 = 750 instead of 250, which is why getting the ball behind the wall is worth so much: up there it can break a dozen bricks before it comes back down.

Clearing a wall pays 1,000 points times its number — 1,000 for the first, 12,000 for the last, 78,000 for all twelve. Bricks broken by the laser score at ×1, because no ball broke them. The best score is kept in your browser, win or lose, and never leaves your device.

Each wall has its own colour scheme on the same felt, and each one is checked by the test suite for fairness: nothing but metal is unbreakable, and every breakable brick can be reached — a flood fill from the open field, through empty cells and breakable bricks but never through metal or through a gap where two bricks only meet at a corner, has to touch every one. A machine player then clears all twelve walls to prove it in play.

The ball gets faster from wall to wall and never within one. On level 1 it travels 320 units a second across a field 480 wide; each level adds 4.5%, so by level 12 it moves at about 519 — 62% faster.

Because every collision is swept. The simulation runs on a fixed 240 steps a second, whatever your screen's frame rate, and in each step the ball is tested along its whole path, not just where it ends up: the earliest thing it would touch — a rail, the paddle, the face or the rounded corner of a brick — is resolved first, and the rest of the step continues from there. That is why a ball that clips the corner of a brick glances off at an angle instead of bouncing as if it hit flat, and why it never slips between two bricks.

The test suite fires balls in thousands of random directions at twenty times the fastest speed the game ever uses and checks that not one of them ends up inside a brick or outside the field. And because a field of rails and metal can hold a path that repeats forever, a ball that goes 10 seconds without touching the paddle or a breakable brick has its next bounce turned by a few degrees. It only ever acts on a ball that has stopped making progress, so a ball busy breaking bricks behind the wall is never touched. For a different kind of physics, try Pinball; for another arcade game against the clock, Snake.