docs: mdi icons

Author: ericgriffin

docs/superpowers/specs/2026-03-31-scuba-tank-icon-design.md

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+# Scuba Tank Icon Replacement
+
+**Issue:** [submersion-app/submersion#109](https://github.com/submersion-app/submersion/issues/109)
+**Date:** 2026-03-31
+
+## Problem
+
+The current tank icon (`Icons.propane_tank`) resembles a BBQ propane tank rather
+than a scuba tank. This is a cosmetic issue that affects the app's domain
+authenticity for divers.
+
+## Solution
+
+Replace `Icons.propane_tank` with `MdiIcons.divingScubaTank` from the
+`material_design_icons_flutter` package. This icon is designed in Material Design
+style and depicts an actual scuba tank.
+
+## Approach: MDI Community Package
+
+The `material_design_icons_flutter` package is the community extension of
+Google's Material Design icon set. It provides 7000+ icons following the same
+design language. Flutter tree-shakes unused glyphs, so bundle size impact is
+minimal.
+
+## Changes
+
+### 1. Add Dependency
+
+Add `material_design_icons_flutter` to `pubspec.yaml` under `dependencies`.
+
+### 2. Replace Icon References (~21 locations)
+
+Replace all `Icons.propane_tank` references with `MdiIcons.divingScubaTank`.
+
+**Affected files:**
+
+| File | Context |
+|------|---------|
+| `lib/features/tank_presets/presentation/pages/tank_presets_page.dart` | Tank list icons (filled + outlined toggle) |
+| `lib/features/statistics/presentation/pages/statistics_gas_page.dart` | Gas statistics section icons |
+| `lib/features/dive_planner/presentation/widgets/plan_tank_list.dart` | Dive planner tank list |
+| `lib/features/dive_planner/presentation/widgets/gas_results_panel.dart` | Gas results display |
+| `lib/features/dive_log/presentation/widgets/cylinder_sac_card.dart` | Per-cylinder SAC metrics |
+| `lib/features/dive_log/presentation/pages/dive_search_page.dart` | Search filter icons |
+| `lib/features/dive_log/presentation/pages/dive_detail_page.dart` | Dive detail tank sections |
+| `lib/features/dive_log/presentation/pages/dive_edit_page.dart` | Dive edit tank sections |
+| `lib/features/equipment/presentation/widgets/equipment_list_content.dart` | Equipment type icon mapping |
+| `lib/features/equipment/presentation/pages/equipment_detail_page.dart` | Equipment detail icon mapping |
+| `lib/features/equipment/presentation/pages/equipment_set_detail_page.dart` | Equipment set detail icon mapping |
+| `lib/features/equipment/presentation/pages/equipment_set_edit_page.dart` | Equipment set edit icon mapping |
+| `lib/features/settings/presentation/pages/appearance_page.dart` | Settings icon |
+| `lib/features/settings/presentation/pages/settings_page.dart` | Settings icon |
+
+### 3. Outlined Variant Handling
+
+The tank presets page toggles between `Icons.propane_tank` and
+`Icons.propane_tank_outlined` based on edit state. If MDI does not provide a
+separate outlined variant of `divingScubaTank`, use the filled variant in both
+states -- the edit/view state is already conveyed by other UI cues.
+
+### 4. Event Icon String
+
+Update the `eventIconName` string for `ProfileEventType.lowGas` in
+`lib/core/constants/enums.dart` from `'propane_tank'` to `'diving_scuba_tank'`
+for consistency. This string is used as a label reference on profile chart event
+markers, not resolved to `IconData`.
+
+## Out of Scope
+
+- Replacing any other Material icons with MDI equivalents
+- Creating custom icon variants (outlined, rounded, sharp)
+- Adding additional dive-specific icons beyond the tank