From cbfa1745b7ded2f8f3c43ad5b5f5daa02626abf9 Mon Sep 17 00:00:00 2001
From: rene <mail@motocamp.de>
Date: Sat, 28 Mar 2026 20:24:30 +0100
Subject: [PATCH] asciiquarium-ng: initial Python implementation with true RGB
 colors
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Single-file animation engine: Canvas with per-cell true-color, ocean
gradient background, waves, castle, seaweed, fish, shark, jellyfish,
ship, bubbles. No Curses dependency — pure ANSI escape codes.
---
 asciiquarium_ng.py | 716 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 716 insertions(+)
 create mode 100755 asciiquarium_ng.py

diff --git a/asciiquarium_ng.py b/asciiquarium_ng.py
new file mode 100755
index 0000000..1dffb6e
--- /dev/null
+++ b/asciiquarium_ng.py
@@ -0,0 +1,716 @@
+#!/usr/bin/env python3
+"""asciiquarium-ng — modernized aquarium animation with true RGB colors."""
+
+import argparse
+import math
+import os
+import random
+import signal
+import sys
+import time
+import tty
+import termios
+import threading
+from dataclasses import dataclass, field
+from typing import Optional
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Terminal helpers
+# ──────────────────────────────────────────────────────────────────────────────
+
+def truecolor(r: int, g: int, b: int, bg: bool = False) -> str:
+    """Return ANSI true-color escape for fg (bg=False) or bg (bg=True)."""
+    layer = 48 if bg else 38
+    return f"\033[{layer};2;{r};{g};{b}m"
+
+
+RESET = "\033[0m"
+HIDE_CURSOR = "\033[?25l"
+SHOW_CURSOR = "\033[?25h"
+ALT_SCREEN_ON  = "\033[?1049h"
+ALT_SCREEN_OFF = "\033[?1049l"
+CLEAR = "\033[2J\033[H"
+
+
+def move(row: int, col: int) -> str:
+    return f"\033[{row+1};{col+1}H"
+
+
+def terminal_size() -> tuple[int, int]:
+    import shutil
+    s = shutil.get_terminal_size()
+    return s.lines, s.columns
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Color palette
+# ──────────────────────────────────────────────────────────────────────────────
+
+@dataclass(frozen=True)
+class RGB:
+    r: int
+    g: int
+    b: int
+
+    def blend(self, other: "RGB", t: float) -> "RGB":
+        return RGB(
+            int(self.r + (other.r - self.r) * t),
+            int(self.g + (other.g - self.g) * t),
+            int(self.b + (other.b - self.b) * t),
+        )
+
+    def fg(self) -> str:
+        return truecolor(self.r, self.g, self.b, bg=False)
+
+    def bg(self) -> str:
+        return truecolor(self.r, self.g, self.b, bg=True)
+
+
+# Ocean gradient: deep midnight blue at bottom → teal at mid-depth → dark cyan at surface
+OCEAN_TOP    = RGB(0,  60,  80)
+OCEAN_MID    = RGB(0,  40,  70)
+OCEAN_BOTTOM = RGB(0,  20,  50)
+
+# Entity colors
+C_WHITE   = RGB(255, 255, 255)
+C_CYAN    = RGB(0,   220, 220)
+C_GREEN   = RGB(50,  220,  80)
+C_YELLOW  = RGB(240, 200,   0)
+C_ORANGE  = RGB(255, 140,   0)
+C_RED     = RGB(220,  50,  50)
+C_MAGENTA = RGB(200,  80, 200)
+C_BLUE    = RGB(80,  140, 255)
+C_GRAY    = RGB(160, 160, 160)
+C_DARK    = RGB(60,   60,  80)
+C_SAND    = RGB(180, 160, 100)
+C_BUBBLE  = RGB(150, 200, 230)
+C_WAVE    = RGB(100, 180, 220)
+C_SHIP    = RGB(140, 120, 100)
+C_SHARK   = RGB(120, 130, 145)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Canvas: per-cell fg color + character, rendered in one write()
+# ──────────────────────────────────────────────────────────────────────────────
+
+@dataclass
+class Cell:
+    ch:  str = " "
+    fg:  Optional[RGB] = None   # None → no fg escape (use bg color as text color)
+
+
+class Canvas:
+    def __init__(self, rows: int, cols: int):
+        self.rows = rows
+        self.cols = cols
+        self._cells: list[list[Cell]] = [[Cell() for _ in range(cols)] for _ in range(rows)]
+        self._ocean: list[RGB] = []
+        self._build_ocean()
+
+    def _build_ocean(self):
+        """Precompute ocean background color per row."""
+        self._ocean = []
+        for r in range(self.rows):
+            t = r / max(self.rows - 1, 1)
+            if t < 0.5:
+                color = OCEAN_TOP.blend(OCEAN_MID, t * 2)
+            else:
+                color = OCEAN_MID.blend(OCEAN_BOTTOM, (t - 0.5) * 2)
+            self._ocean.append(color)
+
+    def resize(self, rows: int, cols: int):
+        self.rows = rows
+        self.cols = cols
+        self._cells = [[Cell() for _ in range(cols)] for _ in range(rows)]
+        self._build_ocean()
+
+    def clear(self):
+        for row in self._cells:
+            for cell in row:
+                cell.ch = " "
+                cell.fg = None
+
+    def put(self, row: int, col: int, ch: str, fg: Optional[RGB]):
+        if 0 <= row < self.rows and 0 <= col < self.cols:
+            self._cells[row][col].ch = ch
+            self._cells[row][col].fg = fg
+
+    def put_str(self, row: int, col: int, s: str, fg: Optional[RGB]):
+        for i, ch in enumerate(s):
+            self.put(row, col + i, ch, fg)
+
+    def render(self) -> str:
+        buf: list[str] = ["\033[H"]   # move to top-left without clearing
+        last_fg: Optional[RGB] = None
+        last_bg: Optional[RGB] = None
+
+        for r, row in enumerate(self._cells):
+            ocean_bg = self._ocean[r]
+            for c, cell in enumerate(row):
+                # Background
+                if ocean_bg is not last_bg:
+                    buf.append(ocean_bg.bg())
+                    last_bg = ocean_bg
+                # Foreground
+                fg = cell.fg if cell.fg is not None else ocean_bg
+                if fg is not last_fg:
+                    buf.append(fg.fg())
+                    last_fg = fg
+                buf.append(cell.ch)
+            # End of row — no newline needed (cursor wraps), but reset bg to avoid
+            # terminal smearing the last cell's bg color into line padding
+            if r < self.rows - 1:
+                buf.append(RESET)
+                last_fg = None
+                last_bg = None
+
+        buf.append(RESET)
+        return "".join(buf)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Entity base class
+# ──────────────────────────────────────────────────────────────────────────────
+
+class Entity:
+    def __init__(self, row: int, col: int, speed: float = 1.0):
+        self.row = row
+        self.col = col          # float for sub-pixel movement
+        self.speed = speed      # cols per second (negative = left)
+        self.alive = True
+
+    def update(self, dt: float, rows: int, cols: int):
+        """Advance physics. Set self.alive = False to remove."""
+        self.col += self.speed * dt
+
+    def draw(self, canvas: Canvas):
+        pass
+
+    def _offscreen(self, cols: int, width: int) -> bool:
+        c = int(self.col)
+        return c + width < 0 or c >= cols
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Small fish  ><>  or  <><
+# ──────────────────────────────────────────────────────────────────────────────
+
+SMALL_FISH_R = ["><>", "><°>", ">°<>"]     # swimming right
+SMALL_FISH_L = ["<><", "<°><", "<>°<"]     # swimming left
+
+FISH_COLORS = [C_CYAN, C_YELLOW, C_ORANGE, C_GREEN, C_MAGENTA, C_BLUE, C_RED]
+
+
+class SmallFish(Entity):
+    def __init__(self, row: int, col: int, speed: float, color: RGB):
+        super().__init__(row, col, speed)
+        self.color = color
+        forms = SMALL_FISH_R if speed > 0 else SMALL_FISH_L
+        self.body = random.choice(forms)
+
+    def update(self, dt: float, rows: int, cols: int):
+        super().update(dt, rows, cols)
+        if self._offscreen(cols, len(self.body)):
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        canvas.put_str(int(self.row), int(self.col), self.body, self.color)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Big fish  >==[}>  or  <{[==<
+# ──────────────────────────────────────────────────────────────────────────────
+
+BIG_FISH_R = [
+    ["    __  ", ">==[}>  ", "    ~~  "],
+]
+BIG_FISH_L = [
+    ["  __    ", "  <{[==<", "  ~~    "],
+]
+
+
+class BigFish(Entity):
+    def __init__(self, row: int, col: int, speed: float, color: RGB):
+        super().__init__(row, col, speed)
+        self.color = color
+        self.sprite = random.choice(BIG_FISH_R if speed > 0 else BIG_FISH_L)
+
+    def update(self, dt: float, rows: int, cols: int):
+        super().update(dt, rows, cols)
+        w = max(len(l) for l in self.sprite)
+        if self._offscreen(cols, w):
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        for dr, line in enumerate(self.sprite):
+            canvas.put_str(int(self.row) + dr - 1, int(self.col), line, self.color)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Shark
+# ──────────────────────────────────────────────────────────────────────────────
+
+SHARK_R = [
+    "                              __  ",
+    "  =-_  =-_  =-_  ==>|  ,----(  o>",
+    "                          ~~-~    ",
+]
+SHARK_L = [
+    "  __                              ",
+    "<o  )----,  |<==  _=-  _=-  _=-  ",
+    "    ~-~~                          ",
+]
+
+
+class Shark(Entity):
+    def __init__(self, row: int, col: int, speed: float):
+        super().__init__(row, col, speed)
+        self.sprite = SHARK_R if speed > 0 else SHARK_L
+
+    def update(self, dt: float, rows: int, cols: int):
+        super().update(dt, rows, cols)
+        w = max(len(l) for l in self.sprite)
+        if self._offscreen(cols, w):
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        for dr, line in enumerate(self.sprite):
+            canvas.put_str(int(self.row) + dr - 1, int(self.col), line, C_SHARK)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Jellyfish
+# ──────────────────────────────────────────────────────────────────────────────
+
+JELLY_BODY = [" ,., ", "( o )", "|'|'|", "| | |"]
+JELLY_ALT  = [" ,., ", "( o )", "| | |", "|'|'|"]
+
+
+class Jellyfish(Entity):
+    def __init__(self, row: int, col: int, color: RGB):
+        # Jellyfish drift slowly horizontally and bob vertically
+        speed = random.uniform(-0.3, 0.3)
+        super().__init__(row, col, speed)
+        self.color = color
+        self.base_row = float(row)
+        self.bob_phase = random.uniform(0, math.tau)
+        self.bob_amp = random.uniform(0.5, 1.5)
+        self.bob_freq = random.uniform(0.3, 0.7)
+        self.t = 0.0
+        self.frame = 0
+        self.frame_timer = 0.0
+
+    def update(self, dt: float, rows: int, cols: int):
+        self.t += dt
+        self.col += self.speed * dt
+        self.row = self.base_row + math.sin(self.bob_phase + self.t * self.bob_freq * math.tau) * self.bob_amp
+        self.frame_timer += dt
+        if self.frame_timer > 0.5:
+            self.frame = 1 - self.frame
+            self.frame_timer = 0.0
+        if self._offscreen(cols, 5):
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        sprite = JELLY_BODY if self.frame == 0 else JELLY_ALT
+        for dr, line in enumerate(sprite):
+            canvas.put_str(int(self.row) + dr, int(self.col), line, self.color)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Bubble
+# ──────────────────────────────────────────────────────────────────────────────
+
+class Bubble(Entity):
+    def __init__(self, row: int, col: int):
+        super().__init__(row, float(col), speed=0)
+        self.float_row = float(row)
+        self.float_speed = random.uniform(0.8, 2.0)   # rows per second upward
+        self.wobble_phase = random.uniform(0, math.tau)
+        self.wobble_amp = random.uniform(0.3, 0.8)
+        self.t = 0.0
+
+    def update(self, dt: float, rows: int, cols: int):
+        self.t += dt
+        self.float_row -= self.float_speed * dt
+        self.col = self.col + math.sin(self.wobble_phase + self.t * 1.5) * self.wobble_amp * dt
+        self.row = self.float_row
+        if self.float_row < 1:
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        canvas.put(int(self.row), int(self.col), "o", C_BUBBLE)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Seaweed
+# ──────────────────────────────────────────────────────────────────────────────
+
+class Seaweed(Entity):
+    """Stationary swaying seaweed at the bottom."""
+    def __init__(self, row: int, col: int, height: int):
+        super().__init__(row, col, speed=0)
+        self.height = height
+        self.phase = random.uniform(0, math.tau)
+        self.t = 0.0
+
+    def update(self, dt: float, rows: int, cols: int):
+        self.t += dt
+
+    def draw(self, canvas: Canvas):
+        for i in range(self.height):
+            r = int(self.row) - i
+            offset = int(math.sin(self.phase + self.t * 1.2 + i * 0.4) * 1)
+            ch = "(" if (i + int(self.t * 2)) % 2 == 0 else ")"
+            canvas.put(r, int(self.col) + offset, ch, C_GREEN)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Ship (on surface)
+# ──────────────────────────────────────────────────────────────────────────────
+
+SHIP_R = [
+    "    |    ",
+    "    |    ",
+    "  __|__  ",
+    " /     \\ ",
+    "/  * *  \\",
+    "~~~~~~~~~~",
+]
+SHIP_L = [
+    "    |    ",
+    "    |    ",
+    "  __|__  ",
+    " /     \\ ",
+    "/ *  *  \\",
+    "~~~~~~~~~~",
+]
+
+
+class Ship(Entity):
+    def __init__(self, col: int, speed: float):
+        super().__init__(0, col, speed)  # row adjusted in draw
+        self.sprite = SHIP_R if speed > 0 else SHIP_L
+
+    def update(self, dt: float, rows: int, cols: int):
+        super().update(dt, rows, cols)
+        self.row = 0   # always at surface
+        w = max(len(l) for l in self.sprite)
+        if self._offscreen(cols, w):
+            self.alive = False
+
+    def draw(self, canvas: Canvas):
+        for dr, line in enumerate(self.sprite):
+            canvas.put_str(dr, int(self.col), line, C_SHIP)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Waves
+# ──────────────────────────────────────────────────────────────────────────────
+
+class Waves:
+    """Animated wave band at the top of the screen."""
+    def __init__(self):
+        self.t = 0.0
+        self.offset = 0.0
+
+    def update(self, dt: float):
+        self.t += dt
+        self.offset += dt * 4.0
+
+    def draw(self, canvas: Canvas):
+        cols = canvas.cols
+        # Two rows of waves
+        for c in range(cols):
+            phase = (c + self.offset) * 0.3
+            # Row 0: crests
+            ch = "~" if math.sin(phase) > 0 else " "
+            canvas.put(0, c, ch, C_WAVE)
+            # Row 1: troughs
+            ch2 = "~" if math.sin(phase + 1.0) > -0.3 else " "
+            canvas.put(1, c, ch2, C_WAVE.blend(C_BLUE, 0.3))
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Castle (static decoration)
+# ──────────────────────────────────────────────────────────────────────────────
+
+CASTLE = [
+    "              T~~",
+    "              |  ",
+    "             /|\\\\",
+    "     T~~    /_|_\\\\",
+    "     |      |   |",
+    "    /|\\\\    |   |",
+    "   /_|_\\\\   |   |",
+    "   |   |   |   |",
+    "===|===|===|===|===",
+]
+
+
+class Castle:
+    def __init__(self, row: int, col: int):
+        self.row = row
+        self.col = col
+
+    def draw(self, canvas: Canvas):
+        for dr, line in enumerate(CASTLE):
+            canvas.put_str(self.row + dr, self.col, line, C_SAND)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Aquarium orchestrator
+# ──────────────────────────────────────────────────────────────────────────────
+
+class Aquarium:
+    def __init__(self, rows: int, cols: int):
+        self.rows = rows
+        self.cols = cols
+        self.canvas = Canvas(rows, cols)
+        self.entities: list[Entity] = []
+        self.waves = Waves()
+        self.castle: Optional[Castle] = None
+        self.seaweeds: list[Seaweed] = []
+        self.t = 0.0
+        self.next_fish = 0.0
+        self.next_shark = random.uniform(30, 60)
+        self.next_jelly = random.uniform(5, 15)
+        self.next_ship = random.uniform(20, 45)
+        self._setup_static()
+        self._initial_population()
+        self._resize_lock = threading.Lock()
+        self._needs_resize = False
+        self._new_size: tuple[int, int] = (rows, cols)
+
+    def _setup_static(self):
+        # Castle at bottom-right
+        castle_row = self.rows - len(CASTLE)
+        castle_col = max(0, self.cols - 22)
+        self.castle = Castle(castle_row, castle_col)
+
+        # Seaweeds scattered at bottom
+        self.seaweeds = []
+        n_weeds = max(3, self.cols // 15)
+        used_cols = set()
+        # Avoid castle area
+        castle_zone = range(castle_col - 2, castle_col + 22)
+        for _ in range(n_weeds):
+            for _ in range(20):
+                c = random.randint(2, self.cols - 4)
+                if c not in used_cols and c not in castle_zone:
+                    used_cols.add(c)
+                    h = random.randint(3, min(7, self.rows // 4))
+                    self.seaweeds.append(Seaweed(self.rows - 2, c, h))
+                    break
+
+    def _initial_population(self):
+        """Spawn a few fish to start."""
+        for _ in range(4):
+            self._spawn_fish()
+        for _ in range(2):
+            self._spawn_bubble_cluster()
+
+    def _fish_row(self) -> int:
+        return random.randint(3, self.rows - 5)
+
+    def _spawn_fish(self):
+        going_right = random.random() < 0.5
+        speed = random.uniform(4, 10) * (1 if going_right else -1)
+        col = -10 if going_right else self.cols + 10
+        color = random.choice(FISH_COLORS)
+        if random.random() < 0.3:
+            self.entities.append(BigFish(self._fish_row(), col, speed * 0.6, color))
+        else:
+            self.entities.append(SmallFish(self._fish_row(), col, speed, color))
+
+    def _spawn_bubble_cluster(self):
+        col = random.randint(2, self.cols - 3)
+        base_row = random.randint(self.rows // 2, self.rows - 3)
+        for _ in range(random.randint(1, 3)):
+            self.entities.append(Bubble(base_row + random.randint(-1, 1),
+                                        col + random.randint(-1, 1)))
+
+    def _spawn_shark(self):
+        going_right = random.random() < 0.5
+        speed = random.uniform(5, 8) * (1 if going_right else -1)
+        col = -40 if going_right else self.cols + 40
+        self.entities.append(Shark(self._fish_row(), col, speed))
+
+    def _spawn_jellyfish(self):
+        col = random.randint(0, self.cols - 6)
+        row = random.randint(3, self.rows - 8)
+        color = random.choice([C_CYAN, C_MAGENTA, C_BLUE, C_YELLOW])
+        self.entities.append(Jellyfish(row, col, color))
+
+    def _spawn_ship(self):
+        going_right = random.random() < 0.5
+        speed = random.uniform(2, 5) * (1 if going_right else -1)
+        col = -12 if going_right else self.cols + 12
+        self.entities.append(Ship(col, speed))
+
+    def signal_resize(self, rows: int, cols: int):
+        with self._resize_lock:
+            self._needs_resize = True
+            self._new_size = (rows, cols)
+
+    def _apply_resize(self):
+        rows, cols = self._new_size
+        self.rows = rows
+        self.cols = cols
+        self.canvas.resize(rows, cols)
+        self._setup_static()
+        self._needs_resize = False
+
+    def update(self, dt: float):
+        with self._resize_lock:
+            if self._needs_resize:
+                self._apply_resize()
+
+        self.t += dt
+        self.waves.update(dt)
+
+        # Spawn timers
+        self.next_fish -= dt
+        if self.next_fish <= 0:
+            self._spawn_fish()
+            self.next_fish = random.uniform(3, 8)
+
+        self.next_shark -= dt
+        if self.next_shark <= 0:
+            self._spawn_shark()
+            self.next_shark = random.uniform(25, 55)
+
+        self.next_jelly -= dt
+        if self.next_jelly <= 0:
+            self._spawn_jellyfish()
+            self.next_jelly = random.uniform(8, 20)
+
+        self.next_ship -= dt
+        if self.next_ship <= 0:
+            self._spawn_ship()
+            self.next_ship = random.uniform(20, 45)
+
+        # Occasional bubble clusters
+        if random.random() < dt * 0.5:
+            self._spawn_bubble_cluster()
+
+        # Update entities
+        for e in self.entities:
+            e.update(dt, self.rows, self.cols)
+        self.entities = [e for e in self.entities if e.alive]
+
+        for w in self.seaweeds:
+            w.update(dt, self.rows, self.cols)
+
+    def draw(self) -> str:
+        self.canvas.clear()
+        self.waves.draw(self.canvas)
+        if self.castle:
+            self.castle.draw(self.canvas)
+        for w in self.seaweeds:
+            w.draw(self.canvas)
+        for e in self.entities:
+            e.draw(self.canvas)
+        return self.canvas.render()
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Input handling (non-blocking, raw mode)
+# ──────────────────────────────────────────────────────────────────────────────
+
+class InputHandler:
+    def __init__(self):
+        self._fd = sys.stdin.fileno()
+        self._old_settings = termios.tcgetattr(self._fd)
+        tty.setraw(self._fd)
+        import fcntl
+        import os
+        flags = fcntl.fcntl(self._fd, fcntl.F_GETFL)
+        fcntl.fcntl(self._fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
+
+    def read_key(self) -> Optional[str]:
+        try:
+            ch = os.read(self._fd, 1)
+            return ch.decode("utf-8", errors="ignore")
+        except BlockingIOError:
+            return None
+
+    def restore(self):
+        termios.tcsetattr(self._fd, termios.TCSADRAIN, self._old_settings)
+
+
+# ──────────────────────────────────────────────────────────────────────────────
+# Main loop
+# ──────────────────────────────────────────────────────────────────────────────
+
+def main():
+    parser = argparse.ArgumentParser(description="asciiquarium-ng — animated aquarium with true RGB colors")
+    parser.add_argument("--fps", type=int, default=30, help="Target frames per second (default: 30)")
+    parser.add_argument("--no-ship", action="store_true", help="Disable the surface ship")
+    parser.add_argument("--no-shark", action="store_true", help="Disable the shark")
+    args = parser.parse_args()
+
+    frame_time = 1.0 / args.fps
+    rows, cols = terminal_size()
+
+    inp = InputHandler()
+    aquarium = Aquarium(rows, cols)
+
+    if args.no_shark:
+        aquarium.next_shark = float("inf")
+    if args.no_ship:
+        aquarium.next_ship = float("inf")
+
+    # SIGWINCH: terminal resize
+    def on_resize(signum, frame):
+        r, c = terminal_size()
+        aquarium.signal_resize(r, c)
+
+    signal.signal(signal.SIGWINCH, on_resize)
+
+    # Enter alternate screen, hide cursor
+    os.write(sys.stdout.fileno(), (ALT_SCREEN_ON + HIDE_CURSOR + CLEAR).encode())
+
+    try:
+        last = time.monotonic()
+        while True:
+            now = time.monotonic()
+            dt = now - last
+            last = now
+
+            # Input
+            key = inp.read_key()
+            if key in ("q", "Q", "\x03", "\x1b"):
+                break
+            elif key == "p":
+                # Pause: wait for another p or q
+                while True:
+                    k2 = inp.read_key()
+                    if k2 in ("p", "q", "Q", "\x03", "\x1b"):
+                        if k2 in ("q", "Q", "\x03", "\x1b"):
+                            raise KeyboardInterrupt
+                        break
+                    time.sleep(0.05)
+                last = time.monotonic()
+                continue
+
+            aquarium.update(dt)
+            frame = aquarium.draw()
+            os.write(sys.stdout.fileno(), frame.encode())
+
+            # Sleep to hit target fps
+            elapsed = time.monotonic() - now
+            sleep = frame_time - elapsed
+            if sleep > 0:
+                time.sleep(sleep)
+
+    except KeyboardInterrupt:
+        pass
+    finally:
+        inp.restore()
+        os.write(sys.stdout.fileno(), (SHOW_CURSOR + ALT_SCREEN_OFF + RESET).encode())
+
+
+if __name__ == "__main__":
+    main()