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:

Target	Points
Ship	30
Helicopter	60
Balloon	60
Fuel Depot	80
Fighter	100
Helicopter+	150
Tank	250
Bridge	500

A bonus life is awarded every 10,000 points, accompanied by a jingle (listen).

The game has three speed settings that control how fast the terrain scrolls:

Speed	Terrain scroll
Slow	1 px/frame
Normal	2 px/frame
Fast	4 px/frame

See state_speed (speed state), handle_up (accelerate), handle_down (decelerate), advance_scroll (scroll update).

The fuel system governs how long the player can stay airborne:

Mechanic	Rate	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

Key details:

• Fuel consumption speed does not depend on the movement speed
• Low fuel warning triggers when fuel drops below 64
• A "tank full" beep (signal_fuel_level_excessive) plays when fuel reaches 252

See consume_fuel (consumption), add_fuel (refueling), state_fuel (fuel state variable).

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 (state_bridge_player_1 for player 1, state_bridge_player_2 for player 2) is incremented at next_bridge_player_1 and next_bridge_player_2 and is never decremented on death.

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.

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 tank_bridge_check against bridge 7, using the player's progress from state_bridge_player_1 (player 1) or state_bridge_player_2 (player 2). The two paths diverge from convert_tank_to_bank.

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 init_current_bridge for the wraparound algorithm.