trivia.ref

; Trivia about River Raid game mechanics.

[Trivia:targets:Targets]
The player's plane can hit eight types of targets with its missile. Six are
mobile enemies, one is a static facility, and one is a terrain structure:

#TABLE(default targets-table)
{ =h Target       | =h Points }
{ Ship            | 30        }
{ Helicopter      | 60        }
{ Balloon         | 60        }
{ Fuel Depot      | 80        }
{ Fighter         | 100       }
{ Helicopter+     | 150       }
{ Tank            | 250       }
{ Bridge          | 500       }
TABLE#

[Trivia:bonusLife:Bonus life every 10,000 points]
A bonus life is awarded every 10,000 points, accompanied by a jingle
(#LINK(Sound#bonus-life)(listen)).

[Trivia:speedMechanics:Player movement]
The game has three speed settings that control how fast the terrain scrolls:

#TABLE(default)
{ =h Speed  | =h Terrain scroll }
{ Slow      | 1 px/frame     }
{ Normal    | 2 px/frame    }
{ Fast      | 4 px/frame    }
TABLE#

See #R$5F64 (speed state), #R$670A (accelerate), #R$6717 (decelerate),
#R$66D0 (scroll update).

[Trivia:fuelMechanics:Fuel mechanics]
The fuel system governs how long the player can stay airborne:

#TABLE(default)
{ =h Mechanic | =h Rate | =h Duration }
{ Consumption   | 1 unit every 2 frames (~6 units/sec)  | Full tank lasts ~40 sec  }
{ Refueling     | 4 units per frame (~48 units/sec)     | Full refuel in ~5 sec  }
TABLE#

Key details:

#LIST
{ Fuel consumption speed does not depend on the movement speed }
{ Low fuel warning triggers when fuel drops below 64 }
{ A "tank full" beep (#R$6E92) plays when fuel reaches 252 }
LIST#

See #R$6DFF (consumption), #R$6E40 (refueling), #R$5F66 (fuel state
variable).

[Trivia:bridgeProgressOnDeath:Destroying a bridge advances the respawn point without crossing it]
Bridge progress is recorded the moment the bridge is destroyed — not when the
player crosses it. If the player dies before reaching the next bridge, the
respawn still places them past the destroyed one. The counter (#R$5F6A for
player 1, #R$5F6B for player 2) is incremented at #R$623F and #R$6249 and is
never decremented on death.

[Trivia:entitySets:Enemy activation delay after spawning]
Enemies do not move or shoot immediately when they appear — there is a delay
of up to 32 frames before they become active. After the player destroys a
bridge, the delay halves to up to 16 frames.

[Trivia:tankAfterBridge:Tank behavior after bridge destruction depends on the level]
When the player destroys a bridge while a tank on the road survives, what
happens next depends on the current bridge number. On bridges 1–7 the tank
freezes in place. From bridge 8 onwards it continues moving until it reaches
the gap left by the destroyed bridge, then fires shells into it.

The threshold is a single comparison at #R$753A against bridge 7, using the
player's progress from #R$5F6A (player 1) or #R$5F6B (player 2). The two
paths diverge from #R$7525.

[Trivia:bridgeProgression:Infinite loop after bridge 48]
The game has 48 unique bridge sections, each containing 64 terrain fragments.
After the player completes all 48, the game does not end — instead it wraps
around using the formula:

new_bridge = ((progress - 48) mod 15) + 33

This creates an infinite loop through bridges 33-48 (the hardest 15 bridges),
making the game theoretically endless. See #R$68E9 for the wraparound
algorithm.