One-Button Game Mini Hack Entry: Pump-Send - Scoring, tips, and behind-the-scenes
One-Button Game Mini Hack Entry: Pump-Send
Hi everyone! Pump-Send is a side-view mountain bike game on an endless desert pump track. You never pedal: all your speed comes from pumping the rollers, and one button does everything. On the ground, a tap pumps or pops; in the air, it throws you into a backflip.
How scoring works
- You get 1 point for every meter you ride. The run ends if you run out of momentum or crash.
- Every clean backflip is worth 50 points, so one flip equals 50 meters of riding.
- Your score and flip count are shown in the top-left corner.
Definitions
- Pump: A tap while rolling downhill. You push the bike into the slope and gain speed.
- Scrub: A tap at the wrong time (going uphill, or a second tap right after a pump). It costs you a little speed.
- Lip: The rising face just before the top of a hill. It glows yellow.
- Pop: A tap on a glowing lip. It's the only way to get airborne.
- Flip: A tap in the air spins the rider backward. Each full rotation you land counts as one flip. Tap only; don't hold the button.
- Stall: Going too slow for too long. This ends the run.
Physics you'll want to know
- Steeper downhill = bigger pump. A pump on a steep drop gives you a big shove, about a third of your starting speed. On a nearly flat stretch, it does almost nothing. Aim for one good pump on each downhill.
- Scrubs add up. A badly timed tap only takes back about a third of a good pump, but a few in a row can leave you crawling.
- Watch the hills scroll. If the scenery slows down and you're barely making it over the crests, pump now or you'll stall.
- Speed is hang time. The faster you hit a glowing lip, the higher and longer you fly, and the more time you have to finish a flip.
- Spin fades in the air. Each tap adds spin, and the spin slowly dies down. More taps spin you faster, but you have to be wheels-down at the right angle when you touch the ground.
- Land matching the slope. Don't start another flip if you won't finish it in time to land at the right angle.
Quick tips
- Build speed with a few pumps before you try your first flip.
- On a big jump, one tap in the air is usually a full flip. Count, then stop tapping.
- When in doubt, skip the flip: distance points still add up.
- The game gets harder as you go, with tighter pump timing and landing requirements.
Behind the scenes
I built Pump-Send with a team of Claude Code agents: one designed the game, one wrote the tests (113 of them!), one built it, one reviewed the code, and one judged prototypes to help me choose among my four original ideas. The judging turned out to be less useful than I expected, since it was pretty obvious after playing which idea would pan out best. The most interesting lesson for me was about using bots to tune the physics.
Lesson one: the bot was too good
The first bot was simply too good at the game. It predicted where each jump would land and planned its flips accordingly, scoring hundreds of points. Then I took the wheel (err, handlebars) and crashed in seconds.
So I had the agents build a bot that plays like a person. It makes the same decisions, but each tap arrives 100 ± 60 ms late, it waits to see what one tap did before deciding again, and it taps at most 10 times per second. That bot survived a median of 8 seconds and crashed in 17 of 30 rides.
Here's what it uncovered and what I changed:
- A slightly late tap on a lip turned into a backflip spin on a tiny hop. Now you only leave the ground when you tap.
- Riders landed on the next uphill 55–68% of the time. Now a lip glows only if a pop at your current speed will land on a downhill.
- A flat dead zone at every crest turned late taps into scrubs. It's gone.
- Everything runs in gentle slow motion (0.8×), so every timing window lasts 25% longer.
- In most flips, the rider's head went through the ground. Now the rider spins around the hips.
After those fixes, the human-like bot survived a median of 53 seconds with 0 of 30 crashes. "The human-like bot survives at least 30 seconds" is now a permanent test for every new build.
Lesson two: bad players on purpose
Bots that play badly are just as useful. Every build is tested against `idle` (never taps), `spam` (taps every frame), and `masher` (8 taps per second). Each one has to die within 15 seconds or score under a fifth of what the scripted bot scores, so you can't win by ignoring or mashing the button. A `random` tapper rounds out the lineup.
Results for the current build, 20 rides of up to 60 seconds each (a different set of rides from the 30 above, so the human-like numbers differ a little):
+------------+----------------------------+-----------------+--------------+--------------+
| Bot | How it plays | Median survival | Median score | Median flips |
+------------+----------------------------+-----------------+--------------+--------------+
| idle | Never taps | 12.8 s | 40 | 0 |
| spam | Taps every frame | 2.2 s | 1 | 0 |
| masher | 8 taps per second | 2.3 s | 9 | 0 |
| random | Random taps | 6.2 s | 30 | 0 |
| human-like | Smart taps, 100 ms late | 46.3 s | 801 | 8.5 |
| scripted | Smart taps, perfect timing | 51.2 s | 1,391 | 14.5 |
+------------+----------------------------+-----------------+--------------+--------------+
Your turn
What's your high score? Did you beat the human-like bot? I'd love to hear if anyone lands three flips in one jump.
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