A knock down game is one where you launch or throw something at a structure and win by toppling it, usually with a limited number of shots. Bowling is the physical version. On a phone, it means Angry Birds, Crush the Castle, Kitty Kaboom and dozens of others, where you fire at a tower and the collapse does most of the work.
The genre is old, and it’s built on a single satisfying idea: you get one action, and then physics decides what happens.
What makes a game a knock down game? #
Four things show up in nearly all of them:
- A limited number of attempts. Three balls, five birds, four cats. Scarcity is what makes each shot a decision.
- A structure rather than a single target. The interesting part is that the pieces hold each other up, so removing one changes everything.
- Physics you can predict but not calculate. You know roughly what will happen. You don’t know exactly.
- A score or rating that rewards efficiency. Finishing with shots to spare is worth more than finishing at all.
That last point is what separates a knock down game from a shooting game. If you can fire forever, there’s no puzzle. The limit is the design.
The physical originals #
The genre started at fairgrounds and in bowling alleys. Milk-bottle toss, coconut shies, tin-can alley and ten-pin bowling all share the structure: a stack, a limited number of throws, and a score based on how much came down. Carnival versions are famously weighted to be harder than they look, which is its own kind of lesson about center of mass.
Video games inherited the format directly. The projectile changed; the maths didn’t.
Knock down games on mobile #
| Game | What you launch | Cost | Rating |
|---|---|---|---|
| Angry Birds 2 | Birds at pig towers | Free, ads and purchases | 4+ |
| Kitty Kaboom | Cats at robot towers | Free, ads, no purchases | 9+ |
| Crush the Castle: Siege Master | Trebuchet at castles | Free, ads and purchases | Varies |
| Castle Crumble | Explosives and spells | Free | 4+ |
| Royal Smash! | A cannon at towers | Free | 4+ |
| Hit & Knock down | Balls at stacked objects | Free | 4+ |
| Smash Hit | Metal balls at glass | Free | 4+ |
Angry Birds 2 is the most polished, and the one everyone means by “knock down game.” Kitty Kaboom is ours, covered below. Crush the Castle predates Angry Birds: the original reached the App Store in September 2009, and its store page still calls it “the physics projectile puzzle game that started it all.” Hit & Knock down from MOBIRIX is the closest thing to the fairground version, with stacked objects and balls to throw at them. Smash Hit is the outlier, since there’s no structure to topple, just glass to shatter as you move forward.
More options are in best catapult games and best slingshot games.
How a knock down game actually decides what falls #
The physics engine underneath doesn’t know what a tower is. It sees a pile of rectangles and circles, each with a weight, a friction value and a bounciness value, and it checks sixty times a second whether any of them overlap. When they do, it pushes them apart and adjusts their speeds.
A tower stands because friction and contact forces balance gravity. It falls when the arrangement stops balancing, which happens either because a support is gone or because the whole thing leaned past the point where its center of gravity sits over its base. That’s the subject of why tall towers fall over, and it’s the single most useful thing to understand if you want to get better at these games.
Breaking is a separate layer the game adds on top. Engines move things; they don’t smash them. Most knock down games give each block hit points and take damage off based on how fast and how heavy the collision was, then delete the block when it runs out. Full detail is in how physics games work.
A worked example #
Kitty Kaboom is the knock down game we make. Robot vacuums took the cats’ treats, so the cats built a slingshot. You drag back, a line of white dots previews the arc, you release, and you knock robots off towers made of cardboard, wood, glass, brick, metal, soap and battery packs.
Three design choices are worth pointing out because they’re typical of the genre:
- Robots break when they land hard. You don’t have to hit them. Removing what they stand on is usually easier and often takes out several at once.
- Stars measure efficiency, not damage. Three stars go to anyone who clears a level using half their cats or fewer, rounded up, so a tidy two-shot win beats a spectacular four-shot one. The maths is in our three stars guide.
- A separate badge rewards total destruction. The Gold Paw goes to a winning run where every breakable block came down, which pulls in the opposite direction from the stars. Chasing both at once usually fails, so you do two runs.
The twist on the formula is the mid-flight tap. Six of the seven cats have a power you trigger while they’re in the air, which turns a single shot into a choice: explode at the right moment, split into three kittens, slam straight down onto a roof, shatter every glass block within range, dash flat over a wall, or magnetize metal and drag robots off perches.
How to get better at knock down games #
- Aim at what’s holding the target up, not the target. This is the whole game.
- Look for chain reactions first. Explosives, hanging weights and anything that will fall onto something else are worth more than a clean direct hit.
- Hit low and sideways to topple, high and heavy to crush. Force near the base produces rotation; force from above produces collapse.
- Use full power almost always, and change only the angle. Consistency is what lets you learn from a miss.
- Wait for everything to stop. Structures keep settling after the obvious collapse, and a shot that looks like a failure often isn’t.
- Restart early. If the first shot of a three-shot budget goes badly, the efficient run is already gone, and starting over costs nothing in most of these games.
Our slingshot aiming technique guide covers the mechanics of the shot itself.
Frequently asked questions #
What is a knock down game called? #
There’s no single agreed name. Stores and players use knock down, tower smash, demolition, physics destruction and castle crusher more or less interchangeably. Searching any of them turns up the same genre.
Is Angry Birds a knock down game? #
Yes, and it’s the best-known one. You get a limited number of birds, the pigs are protected by structures, and the score rewards finishing with birds unused.
What was the first knock down video game? #
Bowling video games go back decades, but the modern physics-based form is usually traced to Crush the Castle, a browser game from Armor Games that reached the App Store in September 2009, a few months before Angry Birds.
Are knock down games good for kids? #
Many are rated 4+ and involve nothing more violent than cartoon structures collapsing. Check the age rating and the store labels for ads and in-app purchases first; physics puzzle games for kids covers how.
Why are knock down games so addictive? #
Short attempts, instant feedback, and a result you half-predicted but couldn’t calculate. Each shot takes seconds, each outcome is a small surprise, and a failed attempt costs almost nothing. We go into it in why destruction games are so satisfying.